I have an OS46FXi and an older OS50FSR. Have tried both engines in different planes, both with the APC 12.25x3.75 and with a Xoar 12x4 wood. Both engines would spin the props within about 500 rpm, with the 12x4 wood getting the edge. The 50 is slightly stronger on both props. However, I really noticed the weight of the APC, as both engines were slow to spool with the APC, and much snappier with the wood prop. If you're looking for quick throttle response, stick with the wood on these engines. However, I must say, I'm using the APC on the 46 in a Phoenix Models Super Decathlon now, and it works great for that place in general sport aerobatics.