About the Magnum 30 vs the OS 30, a buddy and I both got the Hyperion Hayate 25e and he put a Magnum 30 into the plane and I an OS 30. The difference in power was significant, my Hayate got elevator futter and his was hardly able to fly.To catch up with the OS the Magnum overheated (adjustment to lean). That was very funny. Actually, the Magnum can not turn the same prop as the OS 30. According to the spec sheets the OS has 0,5HP and the Magnum 0,45HP.

To sum up, the OS 30 is a sweet little engine but you should also look at the Saito 40. The Magnum on the other hand is rather on the level of the old OS26.