Keep in mind the cost and the end result in making your decision
The cost=
1) $250 for what you can sell the WE airs for
2) $180 for the Fabcraft Air Chambers
3) $65 For the install service and recharge
4) $30 Round trip for the shipping
==========================
$525 Total
In the end, you will still have a shock that has gone thru 2 valving changes since your first year D-7 was made... They will still be leakdown prone and as such... there is no way to tell if the shocks are at the same pressure levels at rest... there is no Gauge to put on the shock.
To upgrade the WE Air Shock to 2009/10 valving will cost you an additional $50 each on top of the cost of the chambers and service.
With the spring rate chambers on there.. the shocks remain NON-user serviceable as before (that is unless you own the nitrogen charging station and tools)
IMO... The WE air shock is a good Basic lightweight shock, and for 85% of mountain users, it is a great shock for many riders working with a swaybar. If you want to upgrade or change performace of the shock... buy a shock that meets those requirements "out of the box"
IMO... Take that $525 and put it towards a good set of Coilover shocks... I feel the best bang for the buck is the Piggyback chamber, Dual-rate coil-spring, compression adjustable Walker Evans needle shocks from Tri City Perforance(same as used on the 2010 Assault and Rush) at $625 per pair or the Carls Cycles Zero Pros with a higher rate spring.
If the shaft on the WE air is nicked, even slightly, the shocks will leak faster than normal with elevated pressure from a "cranked" spring rate chamber.
Unlike the larger chamber on the Assault WE air... the Fabcraft is mechanically adjustable in the piston on the chamber. By adjusting this chamber up in pressure (screwing the adjustment screw in) you in increase the pressure in the shock which WILL help to control body roll in the sled, but it will also increase the pressure in the shock and make the seals MUCH more likely to leakage. Unlike the the Assault WE airs, the Fabcraft chambers still only offer single rate spring rate as the piston in the chamber is backed up by the mechanical screw and not an adjustable volume nitrogen chamber with a floating piston.
The Fabcraft chambers DO NOT effect the leakdown rate of the shock and should still be recharged every season.
As a note, the Fabcraft spring rate chambers were developed when the WE Air shock was in its first release the new valving has changed the character of the shock greatly but is is still a very basic design of a shock and shoud not be compared to Floats or other sophisticated shocks (eg. Zero pros, Exit, Walker Coil-spring).
I also believe that Fabcraft builds some very high quality parts, some of the highest in the industry, and this is not a bash on their components
Good luck in your decision.
