RE: Flapperons V.S. Spoilerons
Please be careful what you call a Waterfall. In a true Waterfall, the wings aren't even working. The plane should be falling while tail and nose rotate around the wing. There will be a slight deviation from the vertical line due to the intitiation of elevator and blip of throttle to begin the manuever. Gary Seeloff did the best I've ever seen when he was flying his H9 Cap. The Cap would rotate so cleanly around the wing it would carry a full half rotation more before stopping. It would only fall just a hair more than one plane length.
What most people call Waterfalls is nothing more than a super tight inside/outside loop. When you see one performed properly you'll know it without a doubt.
Adam Q