you know dynamat is just going to deaden the flexing of any flat surfaces of the trunk WILL NOT prevent any rattles you have to pay attention to those rattles and see if you can either silicone / some dense foam ( do not use spray foam !! will squeek Under pressure and or buldge out quarter panels / trunk .. THE BEST WAY IS to port through ski hole / armrest / rear deck this will deffinatly increace you bass reflex 10 fold .......... then you would have to dynamat your cab instead of trunk and leave you some room in the trunk for amp rack ETC ................... Have fun !!!! oh and if your looking for a cheaper yet better replacement for dynamat look into HUSHMAT !!
http://www.hushmat.com/