I have installed the Big Bore shocks on my Rustler VXL with 40wt oil and the included progressive rate springs. I really like the idea of the progressive rate springs, but the are too soft on the rear even with the largest preload spacer it sits just below level. Does Traxxas make a stiffer prog rate spring (my springs are white with a red dash on the top). I am getting an aluminum gear case, and I think this sag will get worse. I saw slash prog rate springs with different color dashes on them...are these different stiffnessess (if that is a word)? and will they work on a Rusty? I also have the white stock Bandit rear springs, and Rustler black springs. Does anybody know the progression of these different colors...white, black, red, prog rt blue dash, red dash, black dash?