Talking about props I did some experimenting and found out that 10x6 were not that great as it was really giving me a lot of RPM but little more speed. I feel that a 10x7 is better suited for a 46 2C. I have tested out a 46 with a 12x6, that was fun ... you get decent performance in the mid range but once you go to full throttle, the engine is over loading and there is not much more speed. For me I go for the Bolly 10.5 x 7, those props are nice. The Master Airscrew 11x6 is pretty decent too. For a decent amount of torque I will still stick with your APC12.25x3.75, been running it on my Sukhoi 31 and its fun to pull nice big loops (I don't know how to 3D, hehehe).

Again, all this is subject to the plane design, fuel and engine tuning. A tach is always useful.