The way the finger holes are arranged on the ball surface changes the core dynamics; this will change how the bowling ball hooks down the lane.
There are three different types of bowling grips for bowling balls: conventional, semi-finger tip and finger tip; all other grips of any name (i.e., Sarge-Easter grip, etc.) are derivatives.
In a conventional grip, the bowler's ring and middle fingers are placed into the ball up to the second joint, while in a finger tip grip the ring and middle finger holes are made to accept the bowler's fingers only up to the first joint. Beginner bowlers will start with the conventional grip, as it allows for the bowler the maximum grip on the bowling ball without feeling like he's going to drop the ball.
Semi-finger tip has the bowler placing his fingers between the first and second joints. This grip is of choice for bowlers who want a clean release of the fingers, but also want maximum control. It also generates less hook, as strokers preferred this type of grip. Brian Voss was one of several professionals who used the semi-finger tip grip.
A finger tip grip requires more strength, but allows the bowler to release the ball with more lift, and a cleaner release, giving him more control in how the ball rotates after it is released. Don Genalo, a former professional bowler, used the finger tip grip, but would also place his pointer and little fingers very close together with the other two, allowing his hand to stay behind the ball, while allowing his unusually long fingers to maximize the lift upon delivery.
Sarge-Easter Grip - The Sarge-Easter bowling grip prevents the bowler from putting a heavy side spin on the ball and instead creates more forward rotation of the ball. If you tend to put too much spin on your ball this grip might be the perfect choice. The thumb hole remains the same, but for this grip the middle finger remains at finger tip depth and the ring finger is drilled to the two knuckle depth. The amount of hook using this grip will be less than the fingertip grip.
USBC regulations also allow for up to five holes to be drilled on a bowling ball - with the idea that a bowler can use all five digits to grip the ball.[5] Some bowlers use only the middle and ring fingers, while leaving out the thumb, such as in the case of Jason Belmonte who uses the two-handed method.
Finger Inserts:
http://www.turbogrips.com/products.php
Useful Sites:
http://en.wikipedia.org/wiki/Bowling_ball
http://members.tripod.com/Tips_4_Ten...p_and_roll.htm
http://usbcongress.http.internapcdn....l_WEB_2009.pdf