I would not use an APC prop on that OS 300 FT! That engine requires a huge hole to mount the prop .... somethig like 7/16" or something similar to that. Drilling an APC to that size would remove considerable hub material. More than I would feel comfortable being around. Lots of good wood alternatives out there.

With that said, seems like many APC props are not drilled very accurately and the hole is often off center. The molded recess in the back of the prop is the true center and some APC users make drill jugs that key off that molded hole. Also, many racers that use the smaller props drill the center hole oversize and use bushings that pilot in the molded section to accurately center the prop on the crankshaft.

As for drilling wood props, B&B use to make special piloting drill bits that centered in the stock prop hole. They were expensive though. I just use a versabit, drill from both sides just enough to establish the new hole diameter then use a correct sized drill bit to finish drilling through the center of the hub. Harder to describe than to do but the versabits center themselves very well and keep the hole well centered.