Disclaimer: I am not a ball driller.
First, if your son's track is close to the thumb hole it is a high track not low.
Second, I think that the track is a function the release. Drilling can modify the way the travels down the lane, making it hook sooner or later. It may change the flare, but not the position of the track relative to the thumb hole.
Your son is, as Randy Pederson would say, " Playing up the back of the ball", a very professional release that works well on challenging lane conditions. Given his age and the average he is carrying on challenging lane conditions, I would not recommend having him change anything with out consulting a bronze level USBC certified coach.
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