On my father's '97 Roadtrek 170 neither the original nor the replacement refer fit to Domestic specs in the too-big enclosure, so we had a shop add insulation on top and sides to fill gaps of an inch or two and make it zero-clearance there. That, and a baffle at bottom of coils to better-direct natural convection past coils, up, and out upper vent rather than having hot air swirl along sides and pool on top made a few degrees difference, and eliminated a warm-to-touch inside countertop and the wall adjacent to the refer sidewall. A small fan for coils had been previously added to replacement refer when installed; that did make for quicker initial cool-down and perhaps 3-4 degrees inside refer or freezer temp when in extreme heat and parked. However, too much general airflow MAY prevent proper heating of area the refer burner is trying to heat and cooling will be limited. This happened when driving on the freeway, apparently due to body shape of Dodge Ram Van on which the Roadtrek 170 was based, with one tech thinking there might be a vacuum on upper vent area pulling too much air through. We theorized further fixes but didn't try it. Parked with the sun not hitting refer side of vehicle and below about 90 degrees, everything was fine. These things aren't easy.
Another thing that kept temp a little more even was a twin D-cell fan that sat in door where drinks might go. Fan and motor were tiny and would surprisingly run a month.
