Looks like you reached a solution to your immediate question.
I might add a couple of other wrinkles you may encounter traveling around. We have several sites we like to visit in the fall for leaf peeping that are 8 - 9K feet in altitude. Night temps dip into the low twenties.
As Creativepart alludes, and our manuals confirm, the efficiency curve for our heat pump turns south at about 45 degrees and zeros around 36 degrees.
Unfortunately, the efficiency curve for our propane appliances, furnace and refer, turns south at about 6K feet altitude. In fact, my Norcold manual advises not using the the propane mode above 5500 feet. Even our Mr. Heater advises flying closer to the deck.
What to do? Well, not being pet types, blankets and cuddling get us through to the morning cappucino.
Fair Winds and Following Seas