Sam,
As I said, "By way of comparison,..." don't you think I already knew what you said about the MA prop?
I didn't think it was necessary to spell out the obvious but, in retrospect maybe I should have.

Being that the engine in question is on a funfly and I happen to own four of said engines I have a pretty good idea what runs best on it.

If hover-batics are what he is after a 12X4 would be an excellent choice. An APC 11X6 just happens to be a perfect match for the TT Pro .46 in just about any sport flying application. A 10X6 is not nearly enough prop for the muscle this engine has. The engine will easily whirl a 10X6 reaching maximun eficiency of the combination while not expressing the engine's true potential.
The APC may have been too much prop for the Royal but it is definately not too much for the TT Pro .46. Trust me on this one.

Bob S,
Try an APC 12X4 if you want to hover and have instant acceleration. Top end speed will suffer from such a low pitch prop but vertical and hover-batics are superb. Then again, if your happy with the MA 11X5 stick with it!

Sincerely,
Jeff