I don't have good build pics of the GMC Sierra Denali that is under the TR Members Install Pics under our shop forum-I am sorry. But, essentially you basically face the two subs towards each other with about a 6 inch chamber between them. Slot port the box vent to extend into the cab. Then you can use that accordian seal but it can be much smaller (we usually use about an 8" wide by 5 inch tall. You can get them from Topper King in Brandon custom made.

Best bet is to use a lid (new style ones are really nice), but we have also sprayed the bed/box out with Line-X. The only thing you have to watch with that is to get the box and the bed sprayed out individually. Then assemble it (should be obvious but I wanted to make sure you knew that). The Line-X does tighten up the bass significantly it seems. Do not dynamat the inside of the box-not necessary. You can fiberglass all the seams (or the complete interior of the box if you are feeling froggy) and that will give it another step to ward off moisture damage.

Blow through's are quick and easy. Not many clients go for them anymore but they sure as hell bang when completed. Take your time. Build out the box with the vent extension before you cut through the cab. Listen to it and see if it sounds right first. We use basically one design for everyone that we do and it always sounds good...