I have a question for origonal poster -
what is it that you want to achieve.....
loud bass - that does not vibrate the interior pannels of your car ?
if so = why do you think a good trunk setup will stop the rattling
if you are already getting it from inside the cabbin of the car ???
my vette was the noiziest piece of crap I ever heard when I put a single 12" ported in it.
rattling from every single plastic piece in the whole darn car, I spent about a month
going from piece to piece, removing plastic trim - adding sound deadning to each piece - using double layer where plastic trim meets eachother ( the cause of alot of vibrating sound )
and using blue lock tite on metal to metal screws, and silicone on screws in to plastic for all trim pieces. - the end result is a car that plays low notes with out the annoying rattle sound. it takes a while - but its not hard to do. and its not realley expensive either.
it just takes time and a bit of trial and error to find where the vibrations are coming from and figuring ways to make it quiet. the end result will make you alot happier playing music in your car, I can garontee that. I listen to the whole spectrum of music in mine , from orchestrial - to all out bass tracks - and am verry satisfied.
the only reason I say this - is that I think you might have the wrong idea about why you wish to put your subs in the trunk....
the car will rattle if you have bass. there is no way around that.
only to find the problem and trial and error it till its not annoying anymore.