While 3 blade props look great on these types of planes you may not like it's performance in the air. Slowwer flight more speed braking at idle. It deppends how you fly. To me a 13x7 seems large for a .55ax but you obviously have it working. The 12x6 3 blade should work if you can swing a 13x7 now. They say to go to 3 blade go down one inch in diameter.

PSL: I use an APC 13x4 wide with my 55 AX for 3D flying.