I have broken in the engine now and it seems to run with really great authority, I think once it is leaned out, it will be able to hover my 8lb plane. However, I have one questions, right now I am using a 12 x 6 apc sport prop. At full throttle, the engine is turning so fast that I feel that it's going to rip the plane to bits and pieces. Of course there is also a lot of vibration. I didn't tach it (silly, the spinner broke off after the first flight and I couldn't get it started again) but I wonder if I should be running a bigger prop to slow it down a bit. Does running too small a prop cause any problems?

By the way, the engine was a pain to get started the first time because of the "interference" fit. That's what killed the spinner. The engine jammed so many time and made a terrible terrible sound each time and upon first start up that everyone was like gawking at me and making me feel like I had just committed cardinal sin. Anyway, the engine is sweet now... just what prop?