Why don't you work on it from another angle and look at insulating your engine compartment better. Some engine compartment roofs are built flat and don't allow the heat to escape easily. Monaco had an issue with this for a few years in their Camelot line. The fix was to add a 12 volt radiator fan, like found on small cars, to the engine area and exhaust the heat during hot weather.
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab