Stan:
In my humble opinion, this is nothing more than Palm Reading for shooters. If it works for you, good. If it helps Batha sell a piece of copy, all the better. If it has a physiological basis in reality, great.
But the way I see it (and I've tried what you suggest) BOTH palms of the left hand are facing UP in either case. With only the fingers of your left hand curled a bit more abruptly to hold an O/U forearm.
If your right hand is poised for a straight hand grip, POW or acute pistol grip is immaterial I suppose.
Still, if this theory makes you think you can hit more targets with an O/U, may God bless you... and Chris Batha.
May infinity now open its doors...
