>>> CHP with the back hand only drill. Are you suppose to keep the "L" that is created from your thumb down to your wrist to your forearm throughout the swing or are you suppose to cast your back hand flinging the bathead around?
I'm a little confused on this back hand rotation teaching my son CHP. He's been doing the back hand with the L in the arm at waste high turning the body to turn the bat into the bag with the L shaped arm still there. Is he suppose to be adding any wrist action with his back hand. <<<
Your question regarding 'wrist action' in the back-arm drill is very important in developing the most productive CHP. The short answer is "no." - The wrist should be relaxed and serve as a hinge to allow the bat-head to be accelerated from the pendulum effect of taking the hands in a circular path.
Using the muscles of the forearm to un-flex the wrist applies torque at the handle that is not possible with the two-handed grip. -- If you pick up a bat with one hand, you will note you can keep your elbow still and rotate the bat-head 90+ degrees by just flexing and un-flexing the wrist. However, placing both hands on the bat greatly restricts wrist action.
You can check this out by taking your normal two-handed grip on the bat. Now, place both elbows on a table and note how little you can flex and un-flex the wrist. When lifting your elbows off the table, note that it is the push/pull of the forearms that provides the torque to accelerate the bat-head -- not wrist action.
Once your son is gaining good bat speed from his CHP, he must then learn to apply torque with both hands on the bat. The key is - Can he apply torque to the bat without altering the CHP he has been practicing? - Below is a link to a drill that might help.
Note: Aaron, the young gentleman in the drill, is now a senior and hit the most home runs in CA High School Baseball this year.
CHP & BHT Drill