I'm currently building a GP Ultimate (my first build). I plan on powering mine with an OS 46FX. From everything I've read, I gather that most people favor more power than this, but I'm not looking to hover or do any wild aerobatics. The 46 is rated as 1.62bhp, the Rossi looks like 2.5. I would think that'd be enough - that's comparable to an OS 120FS.

Also, I have read that these kits do build heavy. I expect to have to add weight to the nose.

I'll be interested to see other replies as well.