ANYWAY, I bowled league last night, and it didn't go as smoothly as I'd hoped, but as I identified the problems, they made sense. With the old fit, I'd been keeping my thumbhole pretty tight, but with the new angles in my thumb, it was just causing me to hang up at the release, I had quite a bit of drag just holding the ball and inserting and removing my thumb. I also discovered I'd been gripping harder than I thought, and again, the new angles weren't allowing me to get away with it. Once I made the adjustments, I had a few oops shots here and there, but the ones I got through correctly were much better than I've been throwing recently.
Also confirmed that some of my release issues are reaction related. I've never gotten along with the shot at this house, never felt comfortable. From 1-7 it's dry, on 8-9-10 it steps up pretty sharply, and then is completely flat from 11-11, so it makes it feel like the heaviest volume on the lane is right in the middle of the track. Most shots thrown cleanly into the track are very lazy and soft on the backend, so you have to make sure you catch it at the bottom, but it's a lighter volume so if you move right you still get over/under in addition to pretty early reads. I still shot 700, but a better test will be tomorrow at the other house, the reaction is better and more consistent even though the shot is tighter.