Andy Borgogna recently gave me his RSM electric P-51. Without the power system. I am building one, and have the power system for it, so the plan was to check it all out on Andy's version.

When I started flying the plane, it had all sorts of odd flight characteristic changes. It flew too high, rolled in, and wouldn't stay tight on the lines. After much fiddling around on multiple tries, it suddenly hit me that the plane used to fly on a LH prop, and I had put on a RH one. 

Prop change, and bingo! The old warhorse was back to it's good old self!  All the problems went away, just like that.