Looks sorta like the one I toyed with for awhile last spring. Mine was going to use the hood as a top, like the Magnum Powers cold air divider. But since my hood blanket is removed I couldn't find a way to seal the top off the way I liked. I eventually went back to the Mustang-type box that I got from SCP
Spider, my solution to the problem you're referring to was to cut out the opening on the box to match the opening in the fender, then I sealed around the opening on the bottom with some 1" thick Armaflex.