I put a K&B 61 on mine to get it to tork and the plane only weighted 5 lbs(total)! 12x4 is a good way to go for a prop if the 12.25x3.75 doesnt work. Ive had good luck with the Tornado 12x4's. When you get them, they have plastic crap all over them that you need to sand off, but after you do that and balance them, they work great. I never got to try the APC on any of my 46's, but give it a try.