I'm thinking of getting one of these, but trying to figure out what engine to use. I like the idea of a running a 4 stroke, such as an OS 70, and know where I can get one, that's almost new, for a really good price. However, I happen to have a K&B .61 twister that's looking for a home. I think the twister would be nice, same weight range as the OS 70, but more power. However, I'm not crazy about having the big muffler sticking out. Anyone have any thoughts on picking one engine over the other for this plane?