Yep, I'm all too familiar with the swollen thumb syndrome....I continually battle the same deal myself. My thumb is much larger before I start to bowl, but if I size the thumbhole for the full thumb size, I'll be dropping the ball in a frame or two. And, I like my thumbhole to fit fairly snug, so this compounds the problem.
What I do now to help pre-shrink my thumb is to use several different sizes of vinyl thumb sleeves....I start out with one large enough to work my thumb into rather easily, then I gradually work my way down in sleeve size until I finally get the thumb preshrunk down to the size where it will fit in the thumbhole. I use a total of 4 different thumb sleeves to shrink my thumb down to size....and if I have to wait too long between shots, I'll slip the smallest thumb sleeve back on the thumb again to keep it at the size my thumbhole is set up at.
You can find the vinyl thumb sleeves at Bowler's Choice (
www.bowlerschoice.com) for about $3.00 each.....just pick out the size that you normally use for bowling, and get a couple a step or two larger so that you can gradually shrink the thumb down to size before bowling.
In my case, I start shrinking the thumb down about 30 minutes before I get to the bowling center.....it takes me some time to pull the thumb down to the right size. And yes, if I kept opening up the thumbhole to the largest size necessary, my thumb would just keep on getting bigger!
