>>> Hello Jack, question on bat grip. My son is 16, lefty hitter. We've been experimenting on various grips to get the top hand more involved and steady through out the swing. He basically had the same grip for years, fingers around bat. But we are thinking of putting the bat further back in the palm for the top hand. And leave the bat in the fingers for the bottom hand. We felt that he might be rolling over too soon with both hands having a finger grip and losing power? <<<
I know your concern is the grip but I would like to address your reasons for the change you describe. You state the reason for the change is to get his top-hand more involved. I can assure you that if your son's swing is anything like 95 percent of the high school swings I have analyzed, his mechanics relies far to much on his top-hand with his regular grip.
In fact, being to "top-hand dominant" is the main reason most batters never reach their hitting potential. To understand why this is true, one must understand how torque is applied at the handle and its importance in generating bat speed. Basically, torque results from two forces being applied from opposing directions that causes an object (a bat in this case) to rotate about a point.
I may be able to explain why being top-hand dominant can not maximize bat speed with the analogy of turning a nut with a 4-prong tire wrench. Let us assume a tire is lying flat on the ground and you were attempting to loosen a nut with the wrench. To apply maximum torque to turn the nut, you would drive your right hand (or top-hand) forward while pulling back equally with the left (or bottom) hand.
"Pulling back equally" is the key thing to note in rotating the nut or a bat-head. Just driving forward with the back-side is not sufficient. However, in the baseball swing, many (if not most) coaches teach batters to extend 'both' hands approaching contact. It should be obvious from the wrench analogy that both hands moving forward produce little to no torque. Even driving the top-hand past a stationary or slowing moving bottom-hand would produce far less than the desired results.
I will place below a couple video clips that addresses this issue.
Burrell & Bonds -- BHT
Analyizing Bottom-Hand Torque