Something to remember. After drilling is completed, you are only allowed to have a maximum of 3oz of topweight left in the ball.
If the ball starts out with 4 1/2oz, and you drill out 2-2 1/2oz with the finger and thumb holes, that is going to leave you with 2-2 1/2oz topweight already in the ball, and this will all but eliminate the ability to drill the motion hole and have the ball remain "legal".
Drilling the finger and thumb holes deeper to eliminate more topweight MIGHT be effective, but by Mo's theories, drilling the holes deeper may have undesirable effects that would not be "fixable" by the addition of the motion hole.
Would have been better if the ball didn't have so much topweight to begin with, especially if you are wanting to drill a motion hole ball.