has anybody done this or does the ball have to be nib becasue since this driling maximizes core dynamics should the core be new or would it be ok to use this drilling on a ball u want to redril

There is absolutely nothing wrong with doing a double thumb drilling on a ball that has been plugged. The only problem is that since it has been previously drilled, the MB (mass bias) or PSA would have changed. To solve that problem you need to find a pro shop that has a MoRich Determinator, which if you dont know, is a device that will spin the ball and find its new PSA or MB. Once you do that, you can go ahead and work with your double thumb drilling.
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