I want to build a sealed box behind the back seat of my 08 Dakota Crew Cab. There is VERY little space back there, to the point that to get my airspace, I need to get rid of the back wall of the box. My idea is to use some damplifier pro or spectrum sludge on the cab wall to create the back wall of the enclosure. Am I on the right track? Or is there a better way to do this. This is the only location I can use, due to restrictions from my wife.