Got the close-out panels, bit more Dynamat, and went over every inch of sealing everywhere to make sure I don't have any remaining interior air leaks -- except for the doors since I don't have door seals on yet. Body is back on and will be taking it back out this weekend for some more driving! I'll post another video with more detail in the next day or two as well.
I cut the close-out panels from 1/32 aluminum. Screwed and silicone sealed to the chassis, then silicone to the interior tub and sandwiched it with the tub by crimping the rivnuts through both (for the bolts that connect the tub to the body). Even though it's very thin aluminum it's very rigid once it was all screwed together.
I also decided it was going to take too long for me to get a different panel laid out to replace the rear glass and cover my intake, so I went the faster route (I want to drive, dammit!). I cut out a section to clear the intake and I'm actually pretty happy with how it turned out. I still need to clean up the edges a bit, but the shape flows well with the intake and still looks pretty clean since the intake is already black. Looks better in person than in the pics because of all the glare from my garage lights. If you don't like it I don't want to hear about it