To the OP...
I ride BC, 6-9000'. My sled is a 2013 EVO Big Chute M1100T running straight av gas, guessing about 275-280 hp. The only reason to consider putting 7 tooth drivers on is if I was running a 3" track (which I am), but I geared the sled up to 2.25:1, so my actual final drive is about 2.47:1 (stock 8 tooth gearing is 2.33:1, 7 tooth is about 2.63:1). Why did I gear up? Simply put, I have the hp to turn it, and because EVERYTHING is lined up and true, I don't have belt issues, 1680 miles on the sled (all boosted), might change the belt before next trip if I think about it. I feel that gearing the sled down to mask a clutching or belt issue simply isn't the way to go - you wouldn't put a band-aid on a severed limb to control bleeding...
Give JustBoostIt a call, he'll set you up with what works.