RE: CG Chipmunk mods
I built a no-flaps version first, then flaps. If (when) I build a third it won't have flaps. The flaps were a cool gimmick, but did nothing for flight performance. They'd slow the plane down for landing, but the plane was slow enough without them. And they add weight. I liked the handling of the no-flaps plane more.
The ABS cowl and wingtips worked fine for me, but the wheelpants never did.