RE: Another prop question
WSL:
I run a ac 14 X 4 on my YS 63 and it works well for all 3D. The YS 63 is as strong as your magnum 80. so the prop size should be in the ball park. The 13 is just not enough for the engine. When ever you can, run a prop pitch at 4 for 3D flying. ONly problem you run into is clearance which makes for long landing gear on some planes. When you get up in size to the gassers, things change and the engines require different prop sizes. I still keep theprop pitch as low as possible for engine rpm and quick recovery. ENJOY