Just buy the dynamat for the plate, I am running two 12"s and that is the only real annoying rattle that there is. Unless you are doing something insane there is no reason to do it to the whole entire trunk. Ebay is the cheapest place to get it, and if you can get your friends to buy in too you can get alot for a good price. Otherwise I would just deal with a little rattling.
I have a JL 13W6V2. The license plate and spoiler on my speed 3 rattle a lot, but you won't hear it inside the car. The only thing that rattles inside the car is the hatch cover thingy. Make sure it's fastened tightly to get rid of the rattle.
I have a JL 10W6 in a sealed box in my hatch its a MS3 i dont have any rattle issues (and it hit's hard(boom06)) I have found that alot of rattle comes from vented/ ported boxes. Zoom is right tho about the plate. If you do get rattle cut a plate size peice and heat it up and bond it to the plate it will help did it on my Cobra. Good luck!!
Only rattle I heard outside my car was the rear window wiper. I used sound deadening in my entire cargo area and then lined it with closed cell foam. Did the same on the hatch door. Of course I'm not a "bass head" so I'm not driving my equipment to its full potential.
