depend on the kit, most gp kits I've yet to modofy anything. TF kit about 50-50 on MODS, Sig kits I'm alway changing something but if I have any dought I stick to the plans. On ARF's, I usualy just cuss at em wishing I built it cause everything needs to be redone. Everything from the tank is too low or too high if ya can even get to em, don't like how they routed the pushrods, hardware given is junk anyway.