The quick and easy way to do this, if you haven't already, is pick up a piece of 1/2", or close to it, brass tubing from the LHS and sharpen one end. Then just twist a little and it will cut out the extra that needs to be removed for enlarging the hole. I've used the 7/16" brass tubing, it works excellent and gives you a nice clean hole and is a good size for the futaba connectors.