Years ago I installed a 5000 Btu window-type AC under the bed in the rear of our Burro
. Complicated duct work, holes in the floor only, 2 helper fans. (The detailed description of this install was likely lost in the hack a number of years ago).
About 4 weeks ago we traveled from Portland to the NE corner of North Dakota to visit a friend, intending to meander through Wyoming, Colorado, Utah, etc. on our way back. It was hot, muggy, and buggy, so after ND we cut it short and headed home, resolving to concentrate on the shoulder seasons when we venture too far east. We may have hot weather at times in Oregon, but generally the humidity is more moderate and the mosquitoes do not eat at my allergic wife.
During this trip we opted for the pricier state parks more often, for the hookups. The AC was usually started up as soon as we hooked up, and kept it bearable until the sun was blocked. Then the inside temp started to plunge, as you might suspect.
If time and finances allow I intend to replace the AC with a 10,000 Btu unit, ditch the helper fans, double the intake ducting, ditto for the cool air ducting inside, and vent the hot air outside through one of those frig vents.
For our use, the need to accomplish cool down more quickly
is the key thing, and I have no particular problem with cutting the fiberglass either. While we really don't go camping with the idea of sitting inside that much, there are times when the conditions are a bit much and some relief is needed. That said, the times we used the puny AC we have it was the difference between sweaty exhaustion and quite comfortable existence allowing for the slow cool down.
I have probably a somewhat harsh view of the one-hose portable AC units in that they, as Brian pointed out, suck as much hot air in through various crevices as they deliver coolth. If you plant your body right in front of one it may do you some good, but as for cooling an enclosed space they are about useless. Maybe they should be considered thermal fraud, especially when you analyze what is actually taking place when you run one. There, I've "vented," and I apologize.