In it's basic terms, pin to grip center gives a reference to pin up (above the fingers) pin at fingers, or pin down. The smaller the distance to the grip center, typically the earlier rolling the drill will be - still based on the pin to pap distance. The opposite of that, a larger number typically places the pin above the fingers causing the drill/ball to be later or more angular, based on other characteristics of the ball (cover/core/etc.,). The pin to PAP distance helps dictate flare characteristics as well as core strength. Remember the basics - pins to the right of midline think of stronger/earlier, and pins down think of earlier/smoother...
Hope this helps, there's a lot of generalizations in there
Bill
Bowling Services Unlimited
www.bsuproshops.comVise Inserts Staff