I have my 2002 viper with the hammer time wieghts and heel-x secondary. Raced with them and won every heat without the F-7 in the race. I ran the hammer time wieghts with 4.0 heel, 0 center, and 4.8 to 6.0 in the tip depending on what top speed you shooting for. Dragging or aggressive use the Red spring backshifts great, gray spring for top speed quick, not good for drag race. Secondary shift great would highly recommed it, but what type of performance are u looking to get out of it, trail, hillclimb, boondocking, drag.