I have mine in a H9 Cub. It replaced an Evolution .46NT, so I can make a pretty fair comparison. With the .46 2 stroke, the plane wasn't over powered but it was comfortably powered. I could fly in mild wind without fighting too much or getting worried about stalling in turns and such, but it still flew Cublike at full throttle. I'd say top speed wasn't over 40 mph. Switching to the .52 Magnum, the plane is underpowered very much like a true full scale Cub was. I dasn't fly it in wind that makes the leaves move more than just a little on the trees, and it stays full throttle for the entire flight. I can pull a small loop and can do a roll and a very short stall turn, but vertical performance is pretty much just whatever inertia the plane has before I pull up. Even gaining altitude can be a little stressful, because it can't hold more than just a few degrees of climb without slowing the plane and getting me close to stalling. I am still breaking in the engine (have about 1/2 a gallon through it) so I hope the power improves a little as the ring seats, but I don't expect much. I enjoy the challenge of flying the plane like that, and I like the sound and the long flight times that are possible. But if I wanted this plane to perform even basic aerobatics I would need to move up to a .65 or .70.