not a bad and economical idea.. i actually cut a piece of foam the size of my plate and just put that behind the plate it cut the rattling.

 

It may be the decklid inside the cabin also. I had a huge problem with that and all i did was go to the local arts and crafts store and buy some Poly-Fill and stuff it up in the little holes in the trunk. As for the actuall trunk vibrating, use dynamat Extreme and take off the 10 little Felt covered screws (took me like 5 minutes to find them casue they are so well disguised) and apply the dynamat to bare metal. Make sure you apply it good casue if not it is useless. The last part that rattles is on the outside of the trunk, where you stick your hand to lift the trunk up. It is like 2 little holes for your hand next to the push button opener. Cut 2 small dynamat squares and put them in there. That should cut the rattle out of your trunk.

 

yea i already stuffed my trunk lid with poly-fiber filler (see earlier posts) and it helped a decent amount. the dynamat sounds like a good idea (no pun intended). it will also help redirect the sound back into the cabin instead of straight out the back - so hopefully i wont need to have it on as high. as it is, this kicker amp goes up to 11, but i have yet to get it past 3...