Increase the strength in your fingers, wrist and forearms.
Everyday I workout to increase the strength in my hands and forearms. I've noticed that I can shoot a lot longer standing offhand without getting fatigue in my arms, and my scores went up. I've never had a "limp wrist" failure with any gun.
I think it's an overlooked aspect of shooting in general, but with the little Rohrbaugh, I think strong wrists would make a difference in firing it.