I have a 8" sub in a sealed box mounted from the bottom. I just enlarged the hole to 8" and removed a 8" circle of the insulation from the rear deck carpet so that it can breathe perfectly and you cant see the sub.

2000 SVT Black/Tan #1633/2150 (a few mods) Alpine: CDA-9835, MRV-F540, MRD-M550 PG: TANTRUM-X 6.5 COMP all around. Some people wear Superman pajamas. Superman wears Chuck Norris pajamas. CEL currently: Off