Doesn't matter after contact. Can be either way if it helps you to square it up and hit as hard as you can. You may roll over on the ball or popup if you are trying to acheive an arbitrary post contact position such as 2 hands on the bat or being balanced AFTER contact. Once the ball leaves the bat there is NOTHING more you can do to effect the outcome. So 1 or 2 hands AFTER contact is irrelevant.