Hello; My four star 60 has an old OS 90 four stroke pulling it around. The engine has about as much power as a Saito 80 but it'll swing a huge prop, which I like. The other 4 star 60 that I have seen had a surp' 91 on it, the more power was obvious, he could actually hover it without much effort. I brole the tail off it and haven't got around to fixing it yet. I should take a break from covering the Gee whiz Bee, and make up a new tail. I fly at sea level, and know that higher altitude needs more power, but I like the way it flies with the good old 90.