Portable air conditioners?

a bigger roof air

Do some research. Only the dual hose models really help much. Single hose, not much.

Portable air conditioners are not very effective. I have one that was given to me and my son has tried to use it in his room. The problem with the portables is they must use a duct to exhaust a large amount of hot air outside the house or RV. All the air being blown out the window has to be replaced by sucking hot air into the house from outside. So you wind up with a small cooled area in the direct path of the unit. And a larger warmed up area in the rest of the room and/or house.

A better way is probably to find a way to shade the RV or windows.
You could also block out the windows with something.
Try to limit the amount of RV door opening to a minimum to help keep the cooler air in the coach.
Start the AC early in the morning before the heat starts rather than trying to cool after it is already hot.
Adding a second AC unit to the roof is probably your best option.
Or upgrade from a 13,500 AC to a 15,000 AC unit.
Buy a window mount AC unit and some wood and set the unit in an open window. But don't actually use the window to support the unit, instead use a wood frame outside the window.

I bought my Mom a 14K portable AC for her old, uninsulated, 1200 sq/ft open floor plan house and told her to turn it on in the morning before it got too hot.
Naturally she ignored my advice and would wait until she was about to collapse before cranking it up. The amazing thing was it did the job! It never failed to pull the heat down.
If you can plumb the exhaust to the outside, I think it will do a fine job.

A bigger a/c is not plausible as it is already a 15k btu. I'm just trying to think ahead here. Shade is also not really doable in the part of Texas we will be in.

Window AC most bang for buck. Every little bit helps.

I did this 2 years ago. I bought an 8000 btu, single hose to supplement our 13.5k. It works great. In my case, I didn't want to buy the bigger 15k so for $300 it was well worth it. No cooling problems at all even in direct sun in 90* high humidity with 32ft of living space. I also ran a separate 20 amp outside cord. When the weather is cool, I just leave it at home where I also use it sometimes.

Matt1221 wrote:
A bigger a/c is not plausible as it is already a 15k btu. I'm just trying to think ahead here. Shade is also not really doable in the part of Texas we will be in.

Get a second a/c installed.

By far the biggest bang for the buck is to find shade, park there...