Ok, so my current box has issues and it needs a redo. I'm thinking about filling up my trunk completely to the top shelf in the indicated blue shading. BTW thats an old photo and not my current box but it's a good picture of my trunk though.

Now, can I do this successfully for SPL with fiberglass? This will give me 20 cubes and room on that shelf for amps and other things. The next question is about the port, I can figure out dimensions but I'm wondering if it's ok if the port isn't actually in the box. I know external ports work(I use one now successfully) but if it's mounted completely on the outside, meaning no portion of the port will be on the inside of the enclosure, will that work?

Since fiberglass isn't really know for doing great in SPL I was also thinking about laying some 1/4" or 1/2" mdf in the middle of layers. Or maybe some sheet metal. I thought about even some carbon fiber too.

These are my ideas rants and I would really like to know what you guys think.