I can't really answer your questions, but you could, depending on how much room the screw-in inserts leave you, round-over the speaker cut-out with a 3/4" or 1/2" router bit, or front mount with the speaker recessed flush and have a rim piece of 1/8" copper or aluminum water jet cut to cover the gasket and screws painted or clear coated to preference.

This is what I would like to build.
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