The RV guy working on my Trailswest Campster
refused to put in any type of AC in the wall because there is nothing there to support the weight
of it. I also live in Texas where AC is a MUST. Am happy with my 5,000BTU portable AC. We only cut a hole the size of a dryer vent to vent exhaust to the outside (per specs) and a very small hole in floor for drip line for condensation. (I fasten that up under body of trailer for travel & let in down in campsite.) Literally used a dryer vent type of cover on exterior. It has a flap that closes when not in use. Have had to make homemade pieces to angle airflow into the body of the trailer (or it seemed like all the cool air stayed in the kitchenette) but it works in all but the hottest weather in blazing sun. When it's that hot in Texas, I don't go camping!!
I'm not having luck attaching photos, but if you look up my Campster
in the Registry you'll see what I mean.