good luck on the engine purchase. i heard (from Christian) the carb on that engine is a pain to tune. the hyper .21 engines are in the same boat though. an OS would be easy to tune, but not as fast or as cheap.
I'm trying to think where Christian said that. I think he even said it was harder to tune than the hyper. If I find it I'll quote it, but then again, it's just second or third hand info anyway.