Can't tell from the first picture how the speaker mates up with the grill, but if he can acoustically reinforce the trim panel in a way that makes a tight seal around the speaker, he should be able to get pretty close. Should follow almost the same path as sheet metal would with the possibility of many fewer openings. Another possibility that might be easier to get to follow the contours than sheet metal is fiberglass. That's my preference if there's time.Why bother? He's already said he isn't going to close the hole with sheet metal, which means front and rear sound waves will not be kept separated. IB will ****. Of course, Im sure he wont be willing to build sealed/AP enclosures either, so meh, he's bound to have lousy midbass.
