This engine is a monster........plenty of power for hover. Even without the thrustmaster muffler, this thing had unlimited vertical. I'm running a 12.25X3.75 prop @ 14,500 RPM's. The plane weighs less than 4.5 lbs. I was worried about the fuel lines, but they haven't been a problem. The engine is inverted, so I had to do a little adjusting to get the plane to idle correctly. I'm looking into a larger pattern ship now, and for that one I'm going to go 4 stroke, yet I am perfectly happy with my beloved Irvine. It fits entirely inside the cowl with no problem (other than the muffler) Only modification I had to rotate the motor mount slightly to let the muffler sit between the landing gear and wing.