Kai, this is your car right?
http://personal.atl.bellsouth.net/lig/t/c/tcrew/subweb/images/IMG_0087.jpg If I did the 8" in the rear deck, it would be enclosed like his.
But if a single 10/12 would still be better for SQ like everyone said, I can give up some trunk space. I'd prolly put it on the passenger side, up against the back seat.