Carrier low profile units can be 5 degrees nose high and up to 20 degrees nose low on the install. Dometics are similar with regular height units allowing a few more degrees to the high side. You can buy a wedge that goes inbetween the roof and AC to accomodate really sloped roofs. The compressor is horizontal ... dunno how it works, but it does. I have one ... only 7.5" high. I didn't like the regular Dometics like from the factory ... Montana looked like it had a "Derby Hat" sitting on the front of the roof.
