If you can find a good used O.S. 61 it would be your best bet. It is almost the same weight as the 52 but with a bit more HP. A 70 is a good choice, I fly a Mag 70 in a plane desigened for a 45 two stroke. It way overpowers the plane. I initally had a 52 on it and it flew well but I needed 7 oz of weight up front to balance it out. The 70 weighed just shy of 7 oz more than the 52. My plane is about 6 lb, and if I punch it from a slow roll on the runway, I'm 15 ft up 15 ft down the runway. Way over powered. Now if I could just fly it

Don