I flew this several times this weekend (buddy's plane). He had a Magnum .28 with a 9x6 prop. It wasn't very well-powered. I convinced him to run an 8x7 and it made a huge difference. MUCH more power on takeoff and lots more speed. As large as the wingspan is, I wouldn't hesitate to put a 32-36 size engine in it. It is very solidly built and turns like a pylon racer. I am planning on getting one soon to add to my Mini-warbird collection.