To me, the 11x6 is the best all around prop for a .46 BB engine. The 12 X 4 would be ok, and would slow your plane down some--which may be desireable while learning. I'm fairly sure the 12 X 6 would be way too much prop for the .46. The 12 X 4 is pushing it, but some of the stronger .46's (i.e. the AX) can handle it ok. Just may sure you tach it and aren't loading the engine too much.