I think the 50cc engine is a typo. I have a GP Ultimate that weights 15.5 lbs powered by a Fuji 43 and it hauls the Ultimate though most acrobatics with power to spare. The Katana in the ad indicates that it should weight in the 11-12 lb area. Several of our club members fly Nitro Models 71" aerobatic planes in the 11 to 12.5 lb range with G26 gassers.