building inside trunk

fiberglass the joints inside the enclosure.

use mat with the resin.

resin,mat,resin,mat,resin,mat

Attach backing blocks or strips to each panel before you put them in the car, spaced from the edges so that the blocks sit flush up against the adjoining panels. Then you will have joints you can screw or nail together from the inside. As for the glue, I'd strongly recommend gorilla glue, or any other polyeurethane glue, as it will expand to fill any gaps quite nicely. I'm presuming you're not too worried about cosmetics on the parts of the box you won't be able to reach to do the typical cleanup necessary with such glues.

And if you have a good router table, I would also STRONGLY recommend using one of these lock miter joint bits.

They will provide much greater surface area to glue, and help in holding everything together in proper alignment.

I would NOT use gorilla glue, makes a mess and doesn't bond worth a crap. use a good wood glue and caulk the inside seams once it's dry and you'll be airtight.

You could also consider a pocket hole jig for your screw holes. I've never done an in-trunk build, but have done several walls and the main thing is to plan out what/where you can reach and design the box accordingly, so you can glue/screw it together

use good wood glue - tightbond, you can pre assemble the box outside the car - predrill all screw holes with counter sinks, use 2x2 in the corners to get strong braces (alt to fiber glass) and use a good silicone to seal inside box corners. problem with a in car build is if you want to remove it- you have to destroy it.

Cut your sub and port holes before you get it in the car.

Gorilla glue worked great for me when i used it. The only problem was when i came time for a new box it was not easy taking the old one apart.

Gorilla glue will work, but titebond will work better

The way I did mine was to build it outside the trunk first with no glue. I used screws from the inside with a pocket jig http://www.kregtool.com/products/pht/product.php?PRODUCT_ID=30 and put in every single screw. Once done, I took it apart and reassembled it with glue inside the trunk. Worked like a champ.

what type of car do you have

Yes, i find its pretty dumb that mgs and bars can stress people inside the wall and stuff when they are shooting at people outside. What causes this and anyway it can be fixed? Becuase its pretty dumb.