The batman thing just goes in for car club meet stuff.. I still have the original piece. They sound pretty good.. not bad for running line level inputs from the stock deck.
The fiberglass that you see is actually just a cover for the enclosure. Under both of the fiberglass pieces there are actual "enclousres" made from fiberglass with a MDF frame. They are bolted to the floor of the trunk.
Then I built my sub rings that hold the covers in place and stretched the material out the way I wanted it in my trunk. fiberglassed them up.. sanded, sanded, sanded and voila.
I took pictures of the whole process that I am probably going to make into a DIY article. Just need to get the film developed.
The subs are sloped in the way they are so that I can still get full access to my spare tire, and my amp is hidden behind one of the fiberglass covers.