I agree with gilcon and flatspin. clamp it in a press or vise and use a block of wood under the prop to help prevent the drill bit from splintering the wood as the bit exits. useing a drill press helps 100%. 7/16 is the same size as my BME61, It sure pays to take your time here rather than spending alot of time balancing.
Speaking of balancing, How does everyone else balance theirs?
I dip the light end into a jar of colored paint.(after lightly sanding to help paint adhersion.) let dry somewhat,recheck for balance. Adds to safety also.