I tried a half dozen Master Airscrew 10/6 props awhile back and I couldn't get them to balance vertically. The blades would balance no problem with very little work they would hang from 9-3 o'clock on the money, but tip it just a little either way and one side of the hub always wound up on top. I don't think it was an off center hole either, it looked good and to be that far off I am sure it would have been noticeable. The hub needed to be almost ground off on one side to get one to balance, it is beyond being airworthy, but I got frustrated and decided to get it balanced no matter what. I have gone back to APC scmitars and havn't had as much trouble getting them balanced.