Amazing drill! Over rotating is something that has been killing my swing. A good trick you can do to keep from pulling off the ball is to make sure your head does not rotate during the swing. This will lock your lead shoulder in the correct position because in order to over-rotate you have to allow your head to follow your lead shoulder as it opens. If you keep your head on the ball everything else will work naturally including releasing the bat through the ball. Watch any elite hitter and you will see that their head does not rotate with their shoulders while they are swinging.