One other consideration is to put the AC unit on the roof (using an RV unit such as a Coleman). The roof is made for this with the appropriate beams making the 14 inch square opening you need--just Sawzall out the aluminum, drill a few holes, and bolt the unit in place. You'll have to drop the ceiling to run the 120 volt cable, but that's all. Finally, the FB seat goes over where the AC unit is, which is wasted space anyhow.
Jeff
PS: The AC unit I mentioned costs about 700 bucks and is 13,500 BTUs. It does a dandy job of keeping the salon area cool, but "Not so much, narw!" (PA Dutch) in keeping the galley and Vee berth area cool. We use a fan to blow the cool air forward, which helps a bit.
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell