The guy that used to drill my balls used it all the time and never seemed to have a problem.  I use plumbers putty myself which you can just roll between your hands and make any length or shape that you want.
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Proud graduate of Wossanmotta U.

Thanks....
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Shane Soule

yeah.. we use modelling clay (going to guess its exactly the same play-doh with the exception of color).  You can make it any size, its cheap, never had any issues with leaks or anything.   and best part is you don't have to scrape adhesives off the cover of the ball..

S^2
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Joe Theismann's MNF idiot quote of the week:
"Rex Grossman is becoming the player that Lovie Smith thought he was when Smith drafted him."