Take a look at B-quiet ("brown bread"). cheaper than dynamat and nearly as effective. The best thing is that it's lighter than Dynamat. Save your money on the home depot stuff. I have used it....hell anyone that has owned a C5 corvette probably knows about that stuff . It helped some but no enough for the trouble. When I decided to insulate the C6 Z06 I used the b-quiet stuff and it is good stuff. Takes time to apply but it never smelled or lost adhesion. If you are only doing the trunk it won't be expensive at all.