Depends on what kind of layout that you want to put on the ball. I normally like to get my equipment with 4" pins, as my total span is approximately 5". Also, I like to place the pin above the fingers on most of the equipment I drill. If I am going to drill a ball pin down, I will usually go with a shorter (3") pin. Hope that helps some.
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Hook 'em Horns!
"Stats are for losers, I like winning games." - Will Muschamp, Texas Defensive Coordinator