As was said above, get a prop reamer to open up the hole on the prop. [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXK248&P=7]Prop reamer at Tower Hobbies.[/link] . Don't use a drill to open it up if you can avoid it. The problem is that a drill can wander off center and throw the prop out of balance. The reamer will let you open up the hole evenly

Hope this helps

Ken