This is what I did. First buy 2 8" subs that can go in small sealed boxes (.25-.3 cu ft) Kicker Solos are wildly inefficent. I had the Infinity Kappas and was unimpressed. I now have JL 8W3 D4 with dual 4 ohm voice coils wired for a 2 ohm load. I am very satisfied with these. Second, build or have built for you sealed boxes that will fit under the shelf. Mine are trapizoidal to match the angles under there. Third (the scary part) cut two 7" holes in the shelf. One between the seatbelt anchor and the trunk hinge. The other to the outside of the existing hole (in order to make it symmetrical) Fill in the existing hole(I welded in a patch, but I realize that I am crazy) Cut matching holes in the cardboard and carpet cover. Hang the boxes from the shelf. Wire. Enjoy.
In addition to not rattling the trunk, this setup also preserves cargo space. I also have my two Sony Amps hanging from the shelf.
This is an SQ install and will never compete with 10's or 12's with the seat down for SPL.
