i just found this from a guy from the 8 thread...it answers alot of questions................
(A lot of clutch tuning is matching your shoes and springs to your engine/pipe combo and to track conditions. Stiff springs engage later and hit harder, as do light Al shoes. Usually good for tracks with high bite or motors that need help on the bottom. Soft springs engage earlier and composite shoes slip more when they engage. Usually good for loose tracks or engines with a lot of bottom end snap. So, running different shoes and springs changes where the clutch fully engages. Play around with it, you'll be amazed how much changing your clutch setup changes the way the car drives.)