I am trying to come up with a good design for a ported box for a 18" BTL. Now it is going to be in my trunk but I am going to try to get a full 8 cubic feet. It can be 41" wide, 29 inches deep, and the tallest it can be is 18.5" and that is exactly right size for a 18" BTL. The only problem I have had is that I know it is going to need some kind of bracing and since I have no idea how to go about that I don't know how to calculate in the displacement of the extra bracing, and I don't know how to figuire out how big I will have to make my port to be at about 30hz. If it is under 8 which I'm sure it probably will be I'm fine with that I guess, but I need some help on how to get this started.

use some all thread to brace it, or some 1"x1" wood to brace it. i dont think the displacement from that wood would be enough to noticeably tell a difference. might make the box 7.75 cubes or somethin.