I don't know what ALiner has installed in the past, but today Forest River uses the Dometic Cool Cat (about 8000 BTU/hr) in their hard-side folders. The same A/C or heat pump is used by some van conversion (RV Class B) manufacturers.
The Cool Cat is about twice as expensive as the lowest cost 5000 BTU window mounts, but actual sale price ($225-250) is not out of line with price of reasonable quality A/Cs (Kenmore, LG, Frigidaire) of the same size.
I mention this because we've been talking 5000, and since you are going to someplace not only hot, but extremely humid, you might want to take notice of what a manufacturer of a similar hard-side folder thinks is the appropriate size.