Peter, I can't recall any information you might have posted on the grip with the Bertholy's Method. Being a very meticulous teacher he must have very definite ideas on the grip. I am particularly interested in the trail hand grip. Perhaps wrong but expect a transverse grip in the fingers.
The motion of the trail arm, from the top of the back swing, is it largely independent of the trail shoulder ? Is there any specific instruction about the shoulders during the transition ?
Did you have a chance, between all your busy posting on this forum, to actually hit balls with the Bertholy Method in mind ?