We didn't want to modify the trailer and already had a small window unit, so we bought this heater register box that fit perfectly over the AC outlet.
We bent out the edges into a flange and attached it with velcro tape so we could still use it as a window unit.
We then attached a 6 inch dryer vent
And connected it to the upper bunk window using a piece of birch and binder clip.
Final result is ghettotastic