I wonder, not being a driller, but always curious, wouldn't a driller prefer not to drill the finger and thumb holes too deeply for fear of altering the core and its dynamics?
While I have read that drilling a balance hole increase a ball's "reactivity", I have also read that putting that hole on the axis point of inside the axis point will soften the ball's "reactivity". Especially if the hole is wide and shallow, it will not remove core material or a lot of core material.
Since the lanes in my area tend to be drier and I throw a large hook as it is, I have tried not to drill weight holes in my balls in the last few years. If they were needed, I tend to put them on the axis point, because it is supposed to be less reactive.
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"Just because you can do something does not mean you should do it."