A lot to say on this topic!
Bottom line! In the old non insert days, many pro shops as a result of Bill Taylors books used 1/8 left middle finger and 5/8 right ring for righties.
As the inserts came in many drillers went to 3/8 left 3/8 right.
I believe that is a problem. I will get back on this topic!
Sincerely,
Luckylefty