Ball manufacturers add top weight to offset the weight removed by drilling the holes. Most balls come with 2 1/2 - 3 1/2 oz of top weight. This top weight can be used by the driller to create imbalance in the finger/thumb or pos/neg side sectors of the ball by locating the cg away from the grip center. Before the introduction of dynamic cores, ending top weight, finger weight, and/or positive side weight were used to delay the break point and make it sharper. Bottom weight, thumb weight, and/or negative side weight were used to make the ball break earlier and be more "arcy". But with modern balls, the large affect of dynamic core orientation to the ball track has made the affect of imbalance negligible in comparison. So in today's layouts, cg location (which determines imbalance) is primarily used first to help assure the ball's final weights are legal. Then it is also used to allow drilling of an X-hole to modify the dynamics of the core to adjust the ball's reaction while still keeping the final weights legal. The preceding applies to balls with symmetrical dynamic cores. For asymmetrical cores, the imbalance is ignored other than for legality purposes and the mass bias location is used to adjust the ball's reaction. Location of X-holes still applies. -- JohnP
