Brian, what color did you go with? My kit actually came with the under deck piece, maybe it depends on how you order it. I used the DAP Weldwood contact cement on mine. Been 6 or 7 years and no issues yet. Just laid the carpet down like I wanted it, traced it out in lite pencil, rolled the glue out on the floor & carpet, let it dry, and laid it down. Got to be careful though, once the carpet hits the floor, you ain't moving it. I went with the black pipeing around the edge, so the area where the corners meet, I painted black so the hull color wouldnt show. Be sure to watch the grain of the carpet when you do the lids.
Also, be sure to use a fan for air flow when you do under the deck. That glue will mess you up!!!
Its a big project, but sure looks nice when its done.
WARNING!!! You won't be able to keep Lundy of the new Carpet...lol