I am not an expert and you'd need one to verify this. I think you need larger (roughly 1" or more) and deeper (roughly 3") to affect the core size. When you drill into the side of the core and remove weight/mass from it, you're changing the shape and, thus, increasing the RG differential of the
drilled core. This will increase the flare. That will often make a ball hook earlier and more, to a slight degree. It is not a major change, like a pin, a MB or a surface change would be. It is
SLIGHT[/n], in the overall order of things!
KISS or don't sweat the small stuff.
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"None are so blind as those who will not see."
(That includes me too, at times! )