I have kept quiet about this awhile but have been testing a new shock. I have a 156/2.5/16 with Timbersled skid on a Mod XRS. Tom,s Snowmobile built me a custom E-vol rear shock for the Timberskid,This totally changed the performance. These skids tend to buck a bit in the bumps. The E-vol R @ 125/165 lbs just tamed the Mt. Tamer. I set it up with 1/2 sag with rider and it now floats through the bumps.It will not outperform Tom,s Evolution however big gains over the stock shock setup, Last year I installed a extra air tube to the stock shock and relized the enhancments and this addition takes it one step further. He builds a complete shock from scratch with adjustable rebound and personalized valving.All parts from inside /out are new .Tom also indicated there will be an available add on E-vol type chamber for your stock shock for 2010 which will be less costly.He has made many Fox Shox enhancments for all 4 corners and can tune for your style of riding,Jumping or powder