I found a very reasonable solution that fit my needs. I have one 10" and my trunk was rattling (without license plate noise). I went to "Wally World" (aka walmart) and picked up a couple of bags of "polyester fiberfil" in the arts and craft section for about 2 - 3 bucks. I stuffed every major hole I could find, around the lock mehanism and behind the trunk liner.
A considerable decrease in trunk rattle for under $10 (depends on how thorough you are), cant beat that!
If your gonna try it, dont do a half a$$ job and complain. Its a cheap enough alternative that deserves a decent try.
