we didnt try that set up with the masses. but, on mook's sled we did find a real good combo using 01 srx weights (8dn 20??? not sure have to look) and stock primary or daltons red/black primary springs, green secondary spring and a 51-43 dalton helix. it hits 84-8500 rpms with no nasty over-rev and lots of pulling to 100+ mph. we took mooks sled from getting beat by his wife's stock viper by a few sled lengths everytime (both set up identicle only weight differences in rider) to running with her side by side and winning a few times. so it did give it a noticable power gain in efficiancy. ski