I got tired of the damp seatbelts when it rained (and, Ecky's thread shows this mod as reducing noise in motion), so I got the silicone out and did my best to do some tasteful work.
I have it pretty well hidden deep in the cracks, for the most part. Not very noticeable without looking for it, at least.
I started on the enclosure, but nothing to show quite yet. I settled on doing a hybrid of fiberglass and tradition wood. The sides, front, and top will be wood and bottom and rear being fiberglass. This helps maximize airspace, eases installation, and will give the best fit. I should have at least 0.35 cubic foot in the box after bracing and subwoofer displacement, which is perfect for an 8" sub, sealed.