I run the large back strap with the small side panels. I have tried several different combos over the year or so that I have been running the P30 and that seems to he the best combo for me. I have pretty big hands, so that may be the issue, and I grip guns very, very high! I have to radius the back of the slide on Berettas or they will cut me as well. I had the same issue with hammer bite on my Sig 220s when I was shooting those. I would put a really big radius on those hammers as well.
Thanks for the vote on teaching. I am looking forward to it for sure.