I've got a FlyingThingz lawn mower and fly it fairly regular. It has an OS 55 on it and I would say it is terribly underpowered. One thing I would note is the rear wheels. They are set up to flex up when it is rolling on the ground and a small rubber band holds it down in flight. The rubber bands are essential. One snapped on take off and the mower was very unstable and became much more of a handfull than it already is. Make sure they are in place and not about to break. Good luck.