I would try an 11x4 first. The 11x6 will be too much pitch. I used both the 12x4 apc and the 12.25x3.75 apc with a 46fx, and both were very well matched to the airplane. Oh, and what he said, move the cg back on this plane. Before the untimely demise of mine (stupid trees), I had like 3.5 ounces of lead in the tail and was thinking of adding some more.