I might go with one exterior up high. Looking at the second pic in Raz's last post, you can see that there is a double hull behind the stove/sink that goes up to the overhead cabinet. I think there is a couple of inches of empty space between that hull and the outer hull. I could cut a hole in the outer hull about 2 feet above the belly band. That would give a relatively tall air column for convection effect. Warm air in the space behind the fridge
should rise up into that space and out the vent.
I would just need to make sure there is enough opening down low to suck in make-up air for what is venting out the top.
I also need to make sure the space behind the fridge
actually communicates with the space above. Feeling around with my hand it seems like there is a horizontal fiberglass panel that separates the two. Maybe I could drill a bunch of holes in in.
I'm not worried about overheating the unit. I'm not planning to take it to Death Valley in the summer, or to Phoenix. I would just like to not run down my batteries so quickly.