I flew a Goldberg Decathalon with both a saito 150 (way overpowered, shook the forewall loose) then with an OS 91 FX with a pitts muffler. The plane flew very well. I did have to cut back to a 14 X 6 prop though as we have a small field. Landings can be tough if you can't slow it down. The combination had plenty of power. Speed is not the issue for the aerobatics.