I appreciate the input. I'll definitely size down the food and frequency of offerings. I think I stayed with the prey equal to the body size guideline for too long after 500 grams. That's probably why he thickened up so well. I have no problem going back to small rats. Cheaper anyway.
When I feed multiple mice I just wait until the first mouse is all the way down into the belly then offer the next one a minute or two later. You don't want to interrupt all the muscle contractions it takes to move the first mouse down. Give them a minute to get comfortable.