I have mine set up with an OS 91 four stroke. It's just about perfect. I wish I had a bit more authority to pull out of a hover. I'm thinking about switching to the Saito 100.
But my plane comes in under 6lbs dry with the heavy OS! The flight characteristics are great - best plane I've flown.
I was definitely grumbling about some of the build issues, but they were worth it. This is a beautiful plane, and for $205 it was a bargain.