i do not eed 13500 BTUs, as rig is only 22 ft
FWIW I think you do. I have 24' w/ 15K BTU and it only does OK in very hot weather after a hard drive. I think some engine heat winds up in the cabin. Plus the big front van cab is uninsulated in class C. Nice thing about the 13.6 units is they're common and often at the lowest price of any of the AC sizes. I doubt you'd save anything by going to less than 13.6 BTU. What I think you'll need to look for is a sale price AC unit that is compatible with your interior hardware.
If you are into the energy efficient models, friend has the Coleman 13.6 energy saver and I can attest to it's low consumption. He easily runs two off 30 amp with plenty of power to spare. But it wasn't the cheapest 13.6 out there.
