M5james, I used to live in Kirkland, and Seattle, lol. I learned how to fiberglass at the same time Steve Brown (from Alpine) did as one of my best friends lived below him and his wife Amy and taught Steve how to lay fiberglass down. That was when he was working on his MB Quart Celica and later the Acura before he went big time in California.

Anyway, I was just looking at the space and thinking where is this thinking coming from? Because the OEM used a small box, and logical progression leads to figuring out how to use a small enclosure. So much space in there, and woofer technology is a lot better now, than it was in the 90's. That being said, I wonder how 2 8's would sound IB install in the back hatch compartments. I thin I saw a picture of an X5 with and Infinite Baffle sub, but I can not find it.

I had a stand alone kicker box with a 10' and a BSW. I was going to do the same thing you are doing, but was concerned about the limited airspace in that box, and the plastic to resin interface that takes place. I have done this for trim pieces and such, but never anything that needed to be sealed and withstand pressure .