Learning is Occurring
After my last range session, I did a bit of research, and decided to try holding the gun differently. The pro of the new grip is that I seem to be more consistent and it's much more comfortable and doesn't beat up on my weak hand index finger at all.
The downside is that now that I've wrapped my strong hand further around the grip, I can barely reach the trigger in double-action, so I'm reduced to cocking each time to shoot single-action. I can only shoot three shots double before my forearm gives out and I just can't get the trigger back again using the tiny bit of fingerpad that reaches.
BUT, I shot two boxes and was as accurate (it's all relative, okay?) at the end of the session as at the beginning, so that is heartening. Based on the handy-dandy target analysis card provided by the range I think I need to work on a smoother pull.