...by making a fiberglass mold of the rear deck to house a pair of 8s or 10s? It's something I am considering, and seems like it should be a relatively easy thing to accomplish.

I haven't yet removed upper part of the rear deck, just the upper truck cover. Is there anything that would prevent a one piece fiberglass box, made to the same dimensions as the rear deck, from going in there?

Edit: And no, I am NOT talking about a free-air system. I want to do a totally sealed, hopefully two chamber, enclosure.

 

I think you will be better served with the side mounted enclosures instead of the one giant enclosure that I think you are envisioning sitting flush from the trunk floor mat to the top of the rear deck. You lose more trunk space and you get limited to no access to the spare tire. The 4080 box would be my pick for a 10", but if you still insist on doing your own, try to make one like the 4080 box. A better approach IMO. I hope you know how to lay fiberglass and design enclosures. I had a friend do a DIY for kicks and his first project didn't turn out too well. Eventually he had to trash it.

 

Nope, that's not what I'm ensioning. I want to replace the entire rear deck with a similar sized enclosure - basically make a completely stealth enclosure that will not take up any more room that the rear deck does now.

 

It be kinda hard to get enough air space without at least intruding into some of the trunk space. You miiiiiiight get away with 2 8s up there but they'd have to be specifically designed for small enclosures. Forget about a pair of 10s. That entire back half of the trunk is about 1 cuft after it's all said and done and the smallest airspace that i've seen a sub require are Image dynamics and those require a minimum of .3 cuft per 10" sub.

 

With subs mounted to the rear deck, rattling and vibration issues will be crazy even if you find enough volume to accomodate a sub. I think you need to get back to the design board on this.

 

I could live with one 10" (which I will be anyway) with about 400W RMS. But I'm not planning on simply mounting it on top of the stock rear deck. I want to rip that sumobiotch out completely and mold a replica of it in one piece and use it for the enclosure.

But no matter, I've got a 4080 box on the way to me right now. I will, however, remove the stock subs and mount the amp underneath the rear deck somehow and, if needed, mount a fan in each opening in a push-pull configuration. Maybe I'll put the amp on a motorized rack so it can swing down...

Thanks for the input guys, I guess it's back to the drawing board.