Well,my Dalton blk/org spring wrapped 6-1 on stock 35 helix,did not work well for me,except keep rpms around 9000,but on my stm ramps loaded up to 80 grms and ulmer pink primary,it blew my first and only belt. There was slippage,but none you could see,i mean no dirty black marks on either clutch,but I know what slippage sounds like,and what a grenaded belt sounds like at 110 speedo,lol not preety,i got lucky none of it got lodged into either clutch sheeve,but it does make primary clutch at towers look bad. It did run 115 gps early morning on hard packed snow,i had about 2/10,s of a mile to do it in,but it did seem to feel flat on top at that speed. I suspect some of the speed lose was because I did not have my scratchers down,and it was very hard,like ice and I had my track very tight,because it had been racheting some at top speeds. Ok so back to secondary,stm 38 now with ulmers red spring wrapped at 9-1 have not had a chance to test that combo let.