Use a prop reamer to enlarge the holes in a prop. The proplem with using a drill to enlarge the hole it's too easy for the bit to wander as the bit drills out the hole which will result in the hole being off center, which will throw the entire prop out of balance. By using the reamer to enlarge the hole it will stay centered and keep the prop balanced. You can possibly use a drill if you can use a drill press and firmly secure the prop so that it can't move as the hole is drilled out. But if you don't have a drill press use the reamer.

Ken