[Richard]

This is my OPINION. It is not the only option. When I owned 512, with two SCS basement airs, I studied every mini install into a Newell I could find. I went into many of the coaches. Some of them worked well, some of them not so much. I did NOT do an install, so my comments can and should be interpreted as an “internet” expert.

My comments ONLY apply to coaches with SCS units. They do not apply to coaches with roof airs or Dometic split units. My recommended solution is NOT the most energy efficient, since I was not interested in off gridding for very long.

The best and easiest solution that I derived was to use 1 4k condenser unit mounted on the driver side bay coupled with a residential high CGM high static evap unit in the center. Fabricate custom duct work to utilize the existing air intake, and discharge into the existing ductwork for the rear and elephant trunks for the front. Utilize a manually adjustable damper to balance the front and rear air flow since only one air handler is in use. I would also recommend one additional elephant trunk into the front cabin tieing into the front dash air con.

You will find a 4k unit will NOT fit into the existing bay because of height. You will have to fabricate and weld in a 3 inch drop down to allow it to fit. After you remove the SCS you will understand it is not a hard thing to do. No danger of dragging since you are right behind the front tire. There are some that say you do not need 4k with mini efficiency. They do not live with my wife. I agree less capacity will work IF using interior cassettes.

Draw air in from the side and discharge under the coach.

You already have 220 voltage in the supply to the SCS.

The downside of this approach is single point failure. This is a way to use two condensers and two evaps in the same way. PM me if want more details.

Yes there are infinite options. The most energy efficient are the wall mounted cassettes. If your interior cabinetry and your interior decorator can live with that in the coach they cool for the least energy expenditure. My coach would not allow that. If you use wall mounted cassettes you may easily get by with less tonnage. Besides space and aesthetics, some areas may not be cooled as well as others.

Another option is to stash ducted units behind TVs, over cabinets, or in closets. Lots more work in making it fit and running line sets than the basement replacement

Obviously you can cut holes in the ceiling and mount any number of AC or DC units. Pulling wire into the ceiling will be a challenge.

I could go on about everything I considered in my above recommendation, but I will just mention a couple of fundamentals that must be considered with any retrofit.
Physics ——-cool air sinks warm air rises——put your AC discharge on floor level and live to reconsider it’s location
Aesthetics—-although we don’t often think about selling our baby, how will the change I made look
More physics. Coolest air you can get into the condenser unit makes it work better, hence my point don’t pull air off the hot pavement and generator cooling exhaust to route to the condenser.
More physics—the more air you move inside the more comfortable it will be. It doesn’t matter if the air is 33 degrees, if it is not moving the coach will not be comfortable