I previously built a sealed fiberglass box that allowed me to keep my spare. It sounds really good, but I kind of craved more bass. A ported box takes up added space, and after talking extensively with JL Audio I came up with the specs I wanted. The external dimensions are 22"x39" for the bottom piece. The top is the same size as the factory carpet. It is external 5" deep and 3.5" deep internal. The box is only .9 ft^2, so a divider is used to give a storage area. I'll put Fix-a-Flat and other car stuff in there. I'm still waiting on the carpet and terminal, but figured I'd get some pictures posted for anyone interested. Here is how the box will look when installed in the car. A solid flat surface that is sealed from water and carpeted. The sub will downfire and the port is on the top left. The right side is a storage compartment. I'll carpet the interior and put a handle on it. I'm considering using magnets to hold the lid tightly in place. Since this box requires ditching the spare I'll get run-flat tires this summer and use the compartment for Fix-a-Flat and other roadside assistance materials. This is the internals of the box. It houses one JL 10TW3 firing down. At .9 cubic feet the box is larger than the factory recommendation, but I spoke with JL reps that said tuning it to 31 Hz and using a subsonic filter at 28 Hz should allow it to perform well and gain a little extra low end. They aIso said do not go any larger than .9 cubic feet. Other angle showing the depth of the box and the port. For those of you that are interested in the design and theoretical performance here is how it plots in WinISD. The red line is the box I just built. The blue line is the sealed box I had before built to JL factory spec. The green line is a ported box, also built to JL factory spec. These graphs have the subsonic filter set at 28Hz, but I didn't show my low pass filter that is set at 65Hz. I still need to get the terminal to wire the sub, cut a notch in the center bottom of the box where there is a high spot on the floor so the box will sit flat and fiberglass over the high spot, and seal and carpet the entire thing. If anyone wants specific pics let me know. Tomorrow I'll take some of it in the car.