Depends on the quality of the hardware, I've had them leak enough around the threads to ruin a ducted port's tuning, so some form of thread sealant is required to ensure a good seal.

Don't recall ever having any sealing problems between the baffle and t-nut, but then I've always deep seated them by either using washers and a large 'c' clamp or pulling them in with a bolt or using a proper press when available. Just whacking them in with a hammer as I've seen many DIYers do doesn't tend to seat them well, so they typically way over torque the screw to seat them well enough to keep them from falling out when removing the driver and why over time they have become a fastener to be avoided now that threaded inserts have become reasonably priced.

Right, short of needing a high enough stuffing density to require filling the whole cab which requires the back of the driver[s] and any other exposed components to be covered with cheesecloth or similar, anytime stuffing [loose fiberglass batting, polyfil or similar] is used it should always be contained in a suspended cheesecloth or similar 'bag'. This is more effective, ergo requires less stuffing than when lining the walls with it and of course de facto protects any driver[s]/components well enough.

Yes, like all things there's a point of diminishing returns and if too dense a stuffing is used, then it goes from acoustically increasing the cab's effective acoustic volume [Vb], raising F3/lowering Fb and begins decreasing it, raising F3, Fb: http://web.archive.org/web/200210070...ces/fiberfill/

GM