I have exact camper as you
I just got a portable A/C from Lowes They had two different sizes a 11,000 btu ($400.00) and an 8,000 btu($280.00). I got the 11,000 btu because they were out of the 8,000 . If inside garage looking at rear walk in door the window to the left just take sreeen out crank window all the way out which is not much. Stick plastic piece from A/C that has the two hoses on it (one exhaust and one intake) put a dish towel that is folded up one both sides of window to keep bugs out. Plug in under TV And It works great. I have the Happi jac top queen bed/bottom combo that I think will be in the way when in the up postion if I put roof A/C in. I very rarely use upper bed so it stays up against the ceiling blocking lights speakers, and square hole/vent where the A/C would go??
2012 Dutchmen Voltage 3950 epic
1996 F-350 SWD 7.3 Liter Diesel