Charlie Lau - What the critics failed to understand was that the hitter released his top hand only after making contact with the ball. A hitter could actually extend the bat further with one hand, rather than holding onto the bat with both hands. To Lau’s way of thinking, extension mattered more than gripping the bat with two hands after the fact.
You will see batters that typically keep two hands on the bat alter that when having to extend for an outside pitch or for a pitch they misjudged.
If your going to let go, just make sure you are releasing your "TOP" hand. Good luck!