I just got mine up for the first time a few weeks ago.

I have an Magnum 91 that Bill recommended. I like it, it seems like plenty of power, but I will have to admit I've seen a chipmunk at our club that could go a lot faster.

I had to add A LOT of weight to the front to balance it. I didnt' actually determine exactly how much I had to add, but it was several pieces of lead I epoxied to the engine mount.