I usually drill the bolt holes slightly over sized, and rely on the center stud for positioning. I drill all of my props on a drill press.

The most common mistake I see with clicker type torque wrenches is not returning the tension adjustment to zero when not in use, I have seen mechanics with many years experience put their torque wrench back in their tool box still adjusted to a torque setting, which will cause inaccuracy very fast. ALWAYS return the the torque adjustment to zero after use.