If I had to do it over again I would probably just spend the extra to get the Coleman Mach 8 made in America although everyone complains they are noisy outside. The traditional Coleman units are more power hungry.
We are about to install a Mach 8 for our front AC.
One thing I discovered while researching roof airs - the 15k btu Mach 8 actually uses LESS power than the 13.5k btu Mach 8. They gained the extra cooling by adding more coils, and in the end the more powerful unit ends up more power efficient too. This should be a good match for running off of our inverter, though the full-height Mach 3 PS is even more efficient.
I've been researching the noise issue - the biggest concern seems to be that the exterior noise is different than the constant squirrel cage hum of a traditional roof AC. The outside fan only runs when the compressor is on, so it cycles, and is thus more noticeable. But a guy on the Airstream forums tested with a db meter, and on the meter the Mach 8 was actually quieter outside. But... Different, and more noticeable because of the cycling.
I'll let you all know how ours sounds once we get it.