I had a saito 91 on mine, and it just wasn't enough. It would fly great, but long vertical up lines, it would stall out. Pulling out of a hover was real slow.

I now have a ST90 with a moosecan muffler on it, and it pulls out a lot better. Its swinging a 15x4W prop about 1000RPM faster than the Saito 91, and my ST90 isn't completely broken in yet.

when it gets warmer, I will start to realy enjoy this plane,