A 12x5 would be at the outer limits for the 46AX. Mine all seem to be very happy with an 11x6 MAS or APC. I prefer the MAS for the sound. But on my funfliers I do use a 12.25x 3.75 for the extra grunt and thrust for pullouts. It does drop the rpms but my throttle is constantly being played with on the funfliers anyway. I run 5% nitro in all my 2 strokers (.46-.91) and they seem to like it.

Curt