Woody! how did you do it?
I mounted the A/C in the lower galley bulkhead. I then boxed in the rearend of the unit,( leaving the cooling air intakes open on the sides) then ductedthe hot exhuast flow into a 6 inch 120 vac blower then reduced it to 4 inches and piped out the side wall. Why the side wall, I did not want a hole in the floor for water damage or water intrusion when driving. The cooling air comes from inside the lower galley cabinet via vents in the cabinet doors and under the hatch when closed I have a gap and also cut a vent hole in the bulkhead to allow cabin air to be introduced on the cooling side also. I don't have a roof vent, with a window slightly opened, this air exchange allows the unit to cycle longer and aids in dehumidify the air while cooling down the cabin.
I found that if you pull the air from the hot exhuast side it aids in heat removal better than trying to push it through the heat exchanger. The A/C mounted fans installed in most units will not push the cooling air through the heat exchager fast enough with a restriction, they don't like being contained or restricted even a little bit, without the help form a auxillary fan setup pullng air through it would simply over heat and shut down. The main goal here is to have the unit breathe well and do it well for proper operation to prevent overheating and eventually damging the unit itself. The concept is similiar in operation to the image posted, but more compact, so I don't lose all that vauable real estate for storage. I hope this answer your question some what