How much is enough?
You live in Minnesota. There are parts of CANADA that are farther south. How often will you REALLY NEED a second A/C?
Every additional gizmo is something that has to be maintained and eventually replaced.
"STUFF" gets in the way of camping - Cool your A/C to an icebox, and you will reach a point where going outside into heat and humidity - for a campfire, a walk, visiting neighbors, etc. becomes a chore. How many times have you seen a moho pull into a campground and stay for 4 days - and you never see a single occupant put his or her nose outside the door after they get plugged in and set up.
I live in coastal Virginia summer it can easily get to 100 F with 99% humidity. My 13,500 BTU unit runs constantly. I do have a contingency plan for a 3-5 week heat wave when I can't get out of town. It's an auxiliary "window unit"... Cheapo cheapo small unit from the local WalMart or appliance store. I'd pop it in the window over the propane tanks (yep I'd pull out the screen, open the window and make a surround with rigid foam or plywood. Then I'd plug it in directly to the 20 amp hookup so it wouldn't overload any internal circuits.
The old spline and screen could be reinstalled 3 or 4 times before it got too worn, and after that, replacements are cheap. A 5000 BTU window unit can be had for $150 - and carried only in the middle of summer. If I didn't want to store it over the winter, I'd sell it on craigslist for $99 and buy another the next year. Simple and an OPTIONAL option. One less hole in the roof, and one less leak point.
Unless you snowbird, you'll probably need a second A/C three days a season max. A window A/C in the bedroom will cool it down plenty in 10 minutes - and the room will probably stay cool the rest of the night
Today is a gift, that's why they call it the present.