Rapid Roy, the RATZAS chassis has all the adjustment the other do (140 or 150). the first one had 4 springs attached to the tail section, then it went to tail peices with different thicknesses. remember all pan chassis are wide, this limits the body width, thats why i designed my chassis. it really is not top heavy. i have raced ratzas since the beginning. that why i like them so mucn.