Here is the answer from the USBC.. I guess there is a sufficient hole in the bottom of the slug and slug-it combo that goes into the void

Thanks for your question. As far as a void, that is defined in the back of the spec manual as "a manufactured cavity with purposeful size, dimensions and/or location within an object." The spec would be similar to that as applied for a thumb slug. There is no requirement to minimum size of the hole on the bottom of the device. And while small, there is still a clearance through the bottom of the insert for review purposes.

On a similar note: if a thumb hole is drilled into a slug, the clearance through the slug, although most do it, can be any size. If you drill a thumb of 1" into a 1 1/4" slug, you can then drill a small hole through the bottom of the slug to expose the underside. What matters is it's drilled out, but doesn't have to be the same diameter as the thumb hole. when you drill it out, there is no longer a void, even if it's a relatively small hole.

Hopefully this makes sense, but I do understand your concern.
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16-17 mph,350 rpm,PAP 5 1/2 x 3/8up, HighGame 300 x 4, High Series 808
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It is no different than drilling the thumbhole deep to remove excessive thumb weight. Using a 1 1/4 slug for an example you would drill the normal depth and then use a 1 tnch bit to go deeper to remove excessive thumb weigh t. The "shelf" created by the smaller bit wouls linit the slug from sinking. and you would have a "void" under the slug
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just got my email from usbc, all they said was it is approved. Im glad they really took the time to read my email.
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