I'm on baby duty right now because my wife had to have her wisdom teeth removed this morning

But...
Basically I got a 2 inch steel threaded coupling from the electrical section of lowes and paired it with two female threaded and male slip PVC couplings and used a round marine grade electrical outlet plate on each side of the teardrop floor and used silicon caulking to seal it.
So I drilled two 2" holes in the floor of the teardrop then drilled out the center of the round outlet covers with the same hole saw. Then I pre-drilled the screw holes for the outlet covers and caulked the foam baffle on both sides. Screwed in the covers, then caulked the threads of the couplings and screwed them tight. To route "ducting" inside the teardrop I'm just using paneling and running it up the front wall high enough for a tiny air register at a 45* angle to the front and side walls. So the plywood cover for the under bed storage and the corners of the bed will have to be trimmed in the corners, i haven't completed that part yet. But I have the framing for the ducting complete and I've completed the sealed passthrough from the bottom of the trailer.
Make sense? I should probably create a thread in the build section with pictures.