I fight thumb problems all the time. I have a very flat thumb, and clammy, sweaty hands. Whenever it gets humid, I have trouble with the thumb coming out cleanly. The sides of my thumb tend to be the culprit. I make very, very small adjustments using FrankenTape on the sides of the thumbhole now, and this is a big help, but I STILL have troubles some days getting my thumb to cooperate. For me, it's just the nature of having a hand that changes sizes constantly, no matter what kind of span/pitches/etc. I use. (I also use the red Hada Patch and it's a huge help)