Originally posted by harmzuay:
Just thought I'll add to what's been said before:
Chris,
You're not wrong in advising for a slightly larger thumbhole in
view of an expansion of the thumb due to bowling. In fact, its what
most bowlers take for granted and ignore.
However, I'd like to say that the thumbhole issue is touchy.
Firstly, there is a misconception that a larger thumbhole allows a
"cleaner" release. This is
not technically true - the best and smoothest releases come from a
snug fit on the thumb.
This means not too tight, and not too loose (based on experience,
"snug" often feels too tight to players too used to having a
thumbhole way too large for themselves).
The only reason why larger thumbholes have been mistaken to give
cleaner releases is because the bowler is not playing correctly. A
solid, consistent release will not stick in a snug, or even tight
thumbhole. If you expand your thumbhole just to "help" your thumb
exit the ball, you're giving up A LOT of leverage with inproper
technique.
Second: Most balldrillers drill your thumbhole the way its meant to
be. It's always tight because,
1) Immediately after drilling/sanding, the friction makes the thumb
insert expand, thus restricting the space within.
2) They drill it to err on the side of caution - if you find it too
snug, extra sanding can expand it, but not the reverse.
Just keep in mind that everyone's thumb expands differently over a
series of games. Those with bad releases will obviously see their
thumbs swell over even two games. So always go with [b]your
own experience on how to cater for your own thumb.
[/b]
yeah. ur explanation is much clearer than mine.. hee.. thanks
for making this much clearer.. 
As what you said, diff pple expand differently.. in fact, some pple
thumb shrink after playing.. the driller kept saying my thumb will
shrink after playing, tats why he made it smaller, but for me..
mine expand! haha..
about the release, I definately need a bigger hole, cos after the 5
games, i can hear the sound of the air when I put in and out of the
thumb hole.. just like a air tight container. I have to use force
to take my thumb out.. When i threw, the ball struck on my thumb
and results in a late release.. haha.. tats why I made it bigger,
then use the insert tape to make it just nice.. 
