Hey Dan,
Place your thumb in the ball and extend your hand over the finger area. The edge of the finger holes(with or w/o grips) should be about half way between the 1st and 2nd knuckle to be considered a relaxed span. If it is closer to the first joint, it may be a little long plus the possibility of having too much forward pitch which causes your hand to stay in the ball just a hair longer for extra lift at the point of release. Double check the pitches to see if it has too much forward in them. Actually, even if it doesn't have forward pitch, you can redrill them to away pitch for a quicker and cleaner release which may help eleviate some of the finger pressure but you may also have to lengthen the span slightly to compensate. Feel free to contact me directly if you have any further questions, thanks.
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Rick Leong
Ten Pins Pro Shop
Track Amateur/Pro Shop Staff
Vise Grip Staff