So back in December I took on a build to build a box for a '75 Cadillac. It's been a few months and I'm finally nearing completion as my job and clients job intervened. So here we go. There is about 4.4 cubes per sub after port and displacement, bracing and fiberglass resin coat. It is 1.5 inches thick. There will be a 3/4 inch plexiglass viewing window where the hole is.