I tried a few primary and secondary combos with mixed results . First was a.c. primary with cutler adj. 65 grams (i ride around 8 to 10 thousand ft) with stock yellow spring and polaris team red spring in the sec. little snappier on the bottom end but lost some shift out over stock. Next, same prim. change secondary helix to 46/40/34 progressive helix with a orange cat spring, again a little more pull of the bottom but still wouldn't shift completely out. Next new cat primary with titanium spring (same rate as yellow/white), change the sec. to a 10.4 and a RTK torsional kit with a 34/38 helix and a green snopro spring. Pulled better thru the whole range, but still lack full shift out on primary about 7/8 of a inch from top of sheaves,this setup still shock the track pretty hard off acceleration even with 20 thousandth sheave clearance in the primary. Then change to the p85 conv. in prim. and kept the same 10.4 set up in the secondary. Much more consistent pull at take off with out as much track spin but pulled very liner and still seemed to be lacking top end track speed on pulls and subsequently trenching and momentum loss. Lastly, change the sec. back to the 10 inch clutch with the 46/40/36 and orange spring and this was the ticket. Launches of the line with hardly any track spin, pull your arms off as it accelerates and fully shifts out the primary. It climbs way,way better than the previous set up building momentum and not trenching out as you near the top of climb. I know this is a lengthy response to your ? but I feel you should know how I got there, just not by chance, but trying a bunch of combos in every different snow condition possible. And by the way I ride with 5 other m7 and m8 from stock to fully modded and none of their clutch combos preform like this set up does. I've also done many more mods way to many to list big bore/ susp/gearing to name a few but out of all of those the p85 made the most difference. I sound like a salesman for the p85 conversion,but honestly I've spent more money and time on this sled then I care to admit and it finally performs like it should.:face-icon-small-coo