The key is you get a plusher more coil like feel because the spring rate is not over sized because no full stroke ramp up exists with current MTB coil forks.
How can we better make a coil fork even better!

A little history as to how this happened:

  The original or traditional coil forks were designed for for MX and the early MTB forks with a damper and spring in each side, filled about 2/3’s with oil. This allowed the fork to create a coil spring like feel for the first half of the travel. The air space above the oil is compressed which produces an additional spring force in the last half of the travel. This additional air spring effect does two things, it allows the selected coil spring rate to be much softer because the air supplements and increases the spring rate and the ramp up or progression can still be controlled by the air volume compression by changing the oil height.
 MTB forks eliminated one damper to save weight and reduce the cost to produce over the past 20 years and used a single long over rated spring with no oil in the coil leg. This led to an air spring version that emulates a coil to further reduce the  weight.
 This is essentially is where we are now with your typical air spring system single damper front fork.
 Our hybrid coil conversion brings back the ideal coil/air spring system without the added weight of traditional spring/oil filled fork. The air side is still used to create the additional spring rate and ramp rate at a much lower pressure. We use our open bath damper with a lighter and shorter coil spring on top of it. The air spring side remains unchanged and creates the additional spring rate. The air side now uses about 1/3 the pressure that you currently used to create the additional spring rate which can be adjusted to support your weight and ramp up desired. 
 This hybrid system works in conjunction with our open bath custom valved damper with our exclusive midvalve and high speed blow off system (FvAT/HSB). Our damper creates a very supportive compression system that prevents fork dive and still feels plush on small bumps. This midvalve system and base valve will still blow off to prevent deep square edged harshness without bottoming.
 The damper and hybrid spring are $499 and $199 respectively.  The spring weighs about 180-250 grams and the open bath damper weighs within 100 grams of the latest sealed OEM dampers. The optional FvAT/HSB is $99.

Available for Rockshox Boxxer, Fox 40, Fox 49, Bomber 58, BomberZ1 (160/150/140),  Fox 38 (170/160Fox 36 (160/150/140), some Fox 34 and Z2 (150), Pike 29er (2014-17) 150, Zeb (190/170/160), Yari/Lyrik, 160/150/140(riders under 200 lbs). 
MRP (160,150), Bartlett 200.

The air spring side controls the travel but the damper upgrade can accommodate 180-203 travel. Obviously the purpose of a custom valved damper is it would be set up for your current travel and rider requirements. It can be self installed and revalved  by you or your local tuner. If you decide to add the optional hybrid coil spring it would be specific to the travel. Generally as the travel is increased the spring needs to be softer for a given rider weight and obviously longer to accommodate the increased travel. Shipping is about $65.

Coil Shock Tuning Requirements

Maybe I can explain by telling you the three things that are required for proper suspension performance.

1) Proper linear spring rate to support the riders weight at 30% sag based on the starting/average leverage of the linkage.

2) Supportive compression damping that matches the leverage curve and is able to relieve itself on higher speed hits.

3) Progression in the linkage system that speeds up the piston deeper in the stroke to resist bottoming and g-outs, or a band-aid device matched with damping to add progression only to the last 1/3 of the travel. Otherwise the beginning and middle of the stroke will be compromised by an overly stiff or progressive spring.

The issue you have is the leverage of both the Scout and Process 153 are lacking progression needed for a linear coil system. The shocks you are using are unable to produce supportive compression without extreme harshness on squared edged bumps. They are not revalveable and use very small 22 mm non-midvalve designs with only 8/9 mm shafts that can’t support tapered bumper ramp up designs(too small for ours and too weak in our opinion to support these loads)

DB have design issues and only produce crude threshold damping at the expense of rider external adjusters. You need better quality mid and high speed damping which the DB/X2’s can’t produce. It essentially only makes low speed bleed damping and high speed threshold resistance, set too far in and it is harsh, too far out and it is over come too easily and blows thru the stroke. 
The best solution is to use midvalve style pistons with piston/shaft diameters (27-30 mm/12.5-12.7) optimized to displace damping fluid thru a compression adjuster shimmed system, such as a BomberCr, Fox VanRc , RS Super Deluxe/Kage, Push 11-6, and our shocks or similar designs.

Part of the issue is the very progressive linkage works better with more linear shocks like a coil. Even with no bands the Debon air can will still have some progression which will limit the travel. The other issue is higher starting leverage requires higher pressures to set sag properly which also adds to much pressure at the end of stroke which limits the travel. Adding volume to the negative side will help a bit but pressures will still be too higher than desired at the end of stroke. Our SSD/HSB tune will help deep squared edged bumps and provide a higher ride height with more supportive compression that still blows off. Travel will be limited a bit due to air ramp up.
This brings us to a coil shock would be a better choice with this linkage. We would recommend a Fox VanRc/BomberCr tuned by us as a more aggressive solution. 

Fox VanRc/BomberCr

You could purchase a BomberCR (230 x 60/65) no spring and have it drop
shipped to us. typically $300 (do not order a Fox spring)
We would then modify and tune the shock, and supply the proper spring for
your weight.

Tuning $249
Modifications:
Hybrid Progressive coil Conversion Kit $54.95
Hard coated aluminum IFP $29.95
AVA/RS 1.50 inch inside diameter spring $59.95
Your hardware reducers from your old shock you
would transfer to this shock
We can send you an invoice for this build if you wish or you can go online
and fill out the form and shopping cart.

Price will be $499 for the cartridge and requires an
older non ramp air cap to complete the install.
The Ribbon damper is the basic of all dampers out there, it uses gated flow orifice damping, very crude and produces a very firm feel that acts very harsh at speeds, this harshness is relieved by opening the gate(turning the adjuster all the way out)to increase flow but results in no low speed support and now blows thru travel too easily and results in excessive fork dive and bottoming. This requires over springing and excessive ramp up all producing undesirable suspension feeling.

 
We also have developed a few
other improvements to the air ramp system and better lower friction SKF seals
and more durable shrink wrap replacement and position to reduce stiction. We
will also be recommending the correct spring for your weight when using our
cartridge that provides much more compression support without the harsh stock
non-shimmed design.

The stock bushings are really not an
issue, most of the stiction comes from the damper that’s being removed and the
spring that binds in the stanchion due to shrink wrap damage and rollup upon
itself.

The goal of a proper damper is to provide a firm low speed feel that still opens up on small bumps, enough mid speed damping to prevent fork dive without a harsh medium bump feel and enough high speed damping to prevent bottoming while still able to blow-off on high speed square edged bumps. Most of todays dampers have a very firm shim stack with a high threshold to get them to begin to open. This is because the design is based around the pedal platform which needs a very high threshold to prevent unwanted movement in the beginning of the stroke. It also allows heavier riders to be accommodated with the mass production generic valving. Because of this firmer valving system they chose to provide an open or bypass mode to allow the oil to go around these shims. This effectively makes the damper feel softer but at the expense of not allowing low to mid speed damping to be created, i.e. its just a hole. Adding low speed compression helps the fork dive but at the expense of creating a very harsh feel when hitting bumps. Most riders end up with this compromise and settle for this as the best setting that sort of works. As a result of this softer open mode most experience a very soft midstroke, bottoming way too easily and end up adding tokens to prevent this, resulting in a very progressive unwanted feel again.

Our damper modifications and cartridge systems provide the necessary damping circuits for us to valve and set up you suspension properly. In the case of the forks we replace the stock damper with our open bath cartridge. For the rear shocks we have redesigned the internal adjustment systems which allows us to revalve the main piston to properly match your linkage leverage. Each of these systems are set up and designed around descending rather than pedaling, this allows for the main valving systems to meter the damping properly providing a firmer more controlled descent will still maintaining that plush feel. Essentially you can dial in the desired compression damping without that harsh feel, this will provide you with the proper balance between trail and descending.

Upper Shock Link Mounting Bolt = Trek Part # 540755

Lower Shock Link Mounting Bolt = Trek Part # 540756 (Supposedly just
for carbon chainstays, two of # 540755 works if aluminum chainstays)

Upper FOX
shock mounting hardware - 10mm x 60mm - FOX Part #: 803-03-231 

Lower FOX
shock mounting hardware - 10mm x 50mm (offset spacers) - FOX Part #: 803-03-228 or
TREK Part #: 525244 

The open bath is lower cost and all our options fit this damper as well as our hybrid coil system. We can replace the seals and service the spring side, recommend the proper spring and install our cartridge for you.

Cartridge $449
Optional FvAT/HSB $89
Install and set up damper and spring $100
Seals and labor $100
Spring if needed $49

The goal of a proper damper is:

To provide a firm low speed feel that still opens up on small bumps, enough mid speed damping to prevent fork dive without a harsh medium bump feel and enough high speed damping to prevent bottoming while still able to blow-off on high speed square edged bumps. Most of todays dampers have a very firm shim stack with a high threshold to get them to begin to open. This is because the design is based around the pedal platform which needs a very high threshold to prevent unwanted movement in the beginning of the stroke. It also allows heavier riders to be accommodated with the mass production generic valving. Because of this firmer valving system they chose to provide an open or bypass mode to allow the oil to go around these shims. This effectively makes the damper feel softer but at the expense of not allowing low to mid speed damping to be created, i.e. its just a hole. Adding low speed compression helps the fork dive but at the expense of creating a very harsh feel when hitting bumps. Most riders end up with this compromise and settle for this as the best setting that sort of works. As a result of this softer open mode most experience a very soft midstroke, bottoming way too easily and end up adding tokens to prevent this, resulting in a very progressive unwanted feel again.
Our damper modifications and cartridge systems provide the necessary damping circuits for us to valve and set up your suspension properly. In the case of the forks we replace the stock damper with our open bath cartridge. For the rear shocks we have redesigned the internal adjustment systems which allows us to revalve the main piston to properly match your linkage leverage. Each of these systems are set up and designed around descending rather than pedaling, this allows for the main valving systems to meter the damping properly providing a firmer more controlled descent will still maintaining that plush feel. Essentially you can dial in the desired compression damping without that harsh feel, this will provide you with the proper balance between trail and descending.

History of twin chamber cartridges

Yes,  since 1994 when
Suzuki introduced the twin chamber forks to the general public and most of the
high end MX forks have had what you are referring to as sealed dampers.

These dampers are much more complicated than todays so called
sealed bladder dampers. The longer travel and larger diameters forced them to
create a pressurized upper chamber(rod displacement pressure spring IFP reservoir)
that created force on the damper oil in order to prevent cavitation at the
midvalve. The midvalve(back side of the rebound piston) had become the dominate
control of damping on longer travel forks because metering the rod displacement
thru the base valve became too crude and harsh at larger shaft displacements.
The current MTB bladder dampers are using the rod displacement to control damping
with base valves (on top but still referred to as the base valve) to meter and
control lock out with a high flow piston system and threshold damping created
by a rim loaded shim preloaded with a spring referred to as a high speed
adjuster. This simple damping design creates a large amount of resistance to
open the shims, but because of this it acts like a on/off light switch and creates
a harsh feeling until it blows off. Because the harshness is undesirable, the adjuster
is generally run all the way out to relieve this harshness, resulting in very little
damping in the system.

The Push H97 replaces the Trail/Lock part of this circuit
and simplifies the base valve to just a high speed threshold poppet valve and a
low speed adjuster needle. It does not add a midvalve or replace the rebound
piston system. The bladder design is still used to capture the displaced oil,
but is still not pressurized to prevent cavitation. The bladder design requires
that the damper rod be sealed, in fact this seal/seals has become the weak link
and still don’t prevent air ingestion into to damper oil, thus rendering the damper
useless until rebleed. The H97 also suffers from too much threshold as it also
creates a very harsh feel and most riders have to run very little high speed
preload to reduce the harshness resulting in very little to no damping
contribution. This results in more fork dive and reduced bottoming resistance
requiring over springing or adding too much progression to the spring leg.

The twin chamber forks are not actually sealed and contained
stanchion oil for lubrication and hydraulic bottom out. They are also self
bleeding and ingest small amounts of stanchion oil thru the damper rod lip seal
and the oil volume in the damper is reset by the ifp bleed off seal release
during full stroke compressions. This helps prevent accumulated air ingestion
from becoming an issue. This same type of self bleeding is also accomplished by
open bath systems in a very simple way by not completely sealing the damper oil
from the stanchion oil and allowing air to rise thru the rod bushing during use,
yes small amounts of air bubbles are trapped in the damper fluid causing a very
slight emulsion but with todays hydraulic fluids the foaming is almost eliminated.
This is easily accounted for in the valving. The air over oil creates a pressure
on the oil to prevent cavitation and further push out or shrink the air bubbles
to insignificant size thus creating a very consistent and simple damping system
that’s self bleeding. This pressure is also used to add ramp up to the fork resulting
in less tokens in the air side for a more linear midstroke air spring. The
pressure springs also add to the initial spring rate and preload of the initial
feel of the fork reducing the suppleness of the fork. MX bikes are much heavier
so this is not as noticeable.

We actually designed and sold twin chamber dampers for the
Fox 40 cartridge upgrades( http://www.avalanchedownhillracing.com/Fox%2040/Fox%2040%20RC.htm
) for 10 years and have since switched to the open bath design 3 years ago to
simplify the design and also to allow for our hybrid coil system to be used in
the damper side to create the coil conversions for the new air forks that Fox and Rockshox only
sell.

So our open bath system is simple to maintain, adds the much
needed midvalve circuit to the cartridge without cavitation and also lubricates
the stanchion and seals for a much smoother feel.

FVAT/HSB

For the best set it and forget it setup the fvat/hsb minimizes the comprises and gives you less dive, plusher feel without blowing thru stroke on big hits.
If you do both natural trails and groomed and park jump lines it's the best system to minimize compromise

Harsh stock dampers

You have definitely identified the weakness of the fork. The cartridge damping is too harsh to run any compression damping and the air spring cannot create a preload like a coil can so the pull down affect of the negative spring makes the fork too soft in the initial travel which causes packing issue when descending on steep chunk.
The cartridge will solve the compression damping issue with midvalve damping which provides more supportive feel without over damping the base valve.
The air spring issue is solved by adding a coil spring to the damper side and using the air spring at about half the pressure to produce ramp up and additional spring rate needed to support your weight.

Just to be sure that you understand why air forks limit your travel.

This is because the air pressure required to set sag also increases the spring rate at the bottom of the travel and with the air being progressive, this ramp-up makes it impossible to use full travel on rock rough chunk. Setting the sag with preload on a coil spring does nothing to increase the rate of the linear coil spring system. This allows full travel to absorb bumps while the air pressure is used to now to independently add the desired progression.

MRP cartridge upgrade:

Price is $499 for the cartridge and requires an
older non ramp air cap to complete the install.
The Ribbon damper is the basic of all dampers out there, it uses gated flow
orifice damping with a threshold blow-off poppet for highspeed, very crude and
produces a very firm feel that acts very harsh at speeds, this harshness is
relieved by opening the gate(turning the adjuster all the way out)to increase
flow but results in no low speed support and now blows thru travel too easily
and results in excessive fork dive and bottoming. This requires over springing
and excessive ramp up all producing undesirable suspension feeling.  

We offer our custom valved advanced valving damper system like MX and F1
forks have in them for tuning. The coil spring system is adequate for our
upgrade, it is as I said a bit lacking in the in-between spring rates but or
damper allows for much less spring dependence so the medium spring should work
fine.

No need to upgrade the bushings. The stock bushings are really not an issue, most of the stiction comes from the damper that’s being removed and
the spring that binds in the stanchion due to shrink wrap damage and rollup upon itself.
We also have developed a few
other improvements to the air ramp system and better lower friction SKF seals
and more durable shrink wrap replacement and position to reduce stiction. We
will also be recommending the correct spring for your weight when using our
cartridge that provides much more compression support without the harsh stock
non-shimmed design.

The stock bushings are really not an
issue, most of the stiction comes from the damper that’s being removed and the
spring that binds in the stanchion due to shrink wrap damage and rollup upon
itself.

MRP offers a bushing replacement if
needed.

Debonair C1 vs B1

The cartridge will not need any changes. The issue is the choice of Air shaft design. The Debonair B1 will work the best but will not fully extend to full ride height, if this ride height is desired then purchase a 10 longer version. If the height is needed and small bump performance can be sacrificed a bit then the new C1 air shaft will work to hold up the initial travel. We feel our cartridge provides this supportive compression and the C1 is redundant and causes more issues than it’s worth

The hybrid coil is an option that can be added to the open bath damper cartridge:

We offer to improve the air spring system by properly supporting your weight with both the hybrid coil and air spring system combined. In other words you can’t just use the hybrid coil without the open bath damper.
Your issue with the stock damper is that it can’t create supportive quality compression so you are forced to turn it out most of the way and now it blows thru the stroke and bottoms easily which forces you to add tokens and use a higher pressure to prevent fork dive. This chain of events stems from the damper performance and the lack of initial spring rate not developed by the debonair spring. The damper fixes the lack of quality damping and the hybrid coil corrects the initial spring rate and physically corrects the beginning stroke with actual preload on the spring.
The MRP ramp is not going to solve your issues, it only adds adjustable ramp up at the end of stroke with a bit more external control than adding and removing tokens. Too much progression just adds a trampoline affect when bottoming, when you want a more jumping into a swimming pool affect to resist bottoming. Quality damping that’s not harsh,  thru the entire stroke with a more linear spring, prevents the bounce back affects. So a little progression is good but too much resists bumps at the expense of tying to stopping bottoming.
I think you missed the whole point here. The Yari/Lyrik forks have marginal dampers and do not work very well. We sell a upgraded damper to replace them. The hybrid coil option for the openbath damper improves the spring system by creating a coil feel with the air spring system left in tack to create the required ramp up and addition spring force. It cannot be purchased as a stand-alone system