I really Really REALLY want Derek Roddys book but i cant get it here in the UK >
I use the Pearl powershifters and i find the balance to be good and the eliminators are of a higher range so they should be ok.
Im not sure if im telling you stuff you allready know but have you adjusted the springs tension? I remember my old teacher telling me you need to adjust them so when you REST your foot on the pedal the beater should touch the head but I remember seeing a video of Derek Roddy saying he has them as tight as possible.
You also might want to check the condition of all the individual parts. If a nut has no thread left the pedal dosnt move smoothly.
I dont know if ive helped at all mate.