Jim12387,
Without seeing the exact positions of your calluses, areas of swelling, it's hard to tell why you are not coming clean out of the thumb. Could be: span, to long, to short; thumb pitches: to much, to little; finger pitches: to much, to little; timing problems: late, early; muscled swing . . . or a combination of these factors.
I'm a lefty, and these are my specs:
Ring finger: 4.625"; 1/8 reverse, lateral 1/2 left
Middle Finger: 4.75"; 1/8 reverse, lateral 1/8 right
Thumb: 0 lateral, 1/4 reverse; 1" oval thumb sleeve.
I use an oversize sleeve, so I can actually tape left lateral pitch into the thumb, by positioning tape to the leftside of the thumb (looking at the back of your hand.)
It will take a bit of experimenting, but that's what practice is about.
Also: My span is short by about 1/8" intentionally. I use white textured tape on the pad side of the thumb, when my hand shrinks. Normally, if your thumb or fingers shrink, your span has shrunk...time to remove the white tape from front of hole.
If you over-tape the back of your thumb hole, this can cause you to "claw" the grip, which will make you squeeze, stay in the ball too long, topping the ball a bit, and callous up on the inside of your thumb joint.
If you suffer from intermittent foot speed, you will suffer from inconsistent thumb release, do to unintentional "braking" of the thumb release with the inside portion of your thumb.
Just some thoughts....
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Duke Harding
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I'd Rather be Lucky than Good.