I finally got around to moving the trailer out of the shed and taking some picts. Needed to reseal the intake air grilles anyway. Hopefully can get all 5 photos posted. The hood to divert exhaust air through the floor was made out of foil stock used to custom fabricate air ducts, bought at a building supply store. You can cut and bend it relatively easily. I used a few small metal screws to hold it in place, and then used professional duct tape to seal the edges. You can see the spaces on each side for the intake air. And there is about 3/4 inch space on top, which is hard to see in the picture.
I couldn't find a large flexible screened grille to fit the opening, so used a small generic aluminum grill on the bottom, and overlapped it with a larger one on top. Was afraid just the one larger grille on top wouldn't give enough air flow.
This installation is much easier if you have a closet next to the door, as was the install I copied. Working under the fridg is a pain in the neck--and back. I also used sealer and tape to stop the small openings into the cabinet area. I hard wired the unit into the roof AC line and circuit breaker. I would recommend a 6,000 btu AC unit. The 5,000 one has to really work hard when the outside temp gets near 100.