My father and I have been doing exactly this for years.  My fingers swell and shrink quite easily, so this is really the only way for me to combat this.

Has worked well for both of us, so I don't see where it wouldn't work for you.  Give it a try, if you like it great, if you don't, oh well.
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University at Albany 2007
    -Let's Go Danes-

ROTO GRIP - King of Them All
STORM - The Bowlers Company

Harry E. Inglis 3/31/1915 - 2/3/2009

As uwecbowler stated, you can use regular drinking straws. I drill all the my finger holes with a 1" bit about 3/4" deep and then drill to the required 1 3/4" with a 31/32" bit. I glue the front of the insert and just a small bit on each side, leaving the back open.  This gives me a little play for when my fingers expand/contract. If they seem a little big, I just cut a piece of straw about 3/4" long and put it between the insert and the ball. Works great, costs nothing and won't affect your feel.
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Track PBA Regional Staff

http://s318.photobucket.com/albums/mm427/thunder835/Track%20Equipment/

Evolutionary. Revolutionary.
People don't lack strength, they lack will.

I use cut up business cards for shims. I have a small box of them in the bag and a pair of tweezers for taking them out.
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Have no fear of perfection - you'll never reach it.....
Beer for the man, white wine fruit based drink for the lady.
Lane 1 for the man, storm fruit smelling ball for the lady.....
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c(')(')