I built my GP 40 sized CAP 232 with four stroke power in mind from the very beginning. Some that I had seen flown with 40-50 sized 2 strokes were fairly fast (almost too fast) on the straight and level, but I wanted an aerobatic bird that FLEW like a cap, with great vertical and quick acceleration/decelearation. I started with the YS .53 in mine (flew great, but wanted unlimited vertical in hot weather), and then moved up to the YS .63. No problem with it being tail heavy, though if it was, I think I would move the rudder servo out of the tail and back under the wing before I added extra weight in the nose. The thing that worried me about .90 sized four strokes in these planes is the extra weight.

With the CG set where I have mine, I do have to use careful application of up elevator on the take-off roll, to prevent a nose-over on our thick grass field, but it isn't anything I can't handle.

Lee