Close. The hole is to feed the cooler fresh air to the refer only. The furnace will pull outside air in and exhaust it through the furnace inlet/outlet. This is how the did it before they started to go with the louvered doors. I like the hole in the floor better, personally it makes more sense. The Air under the trailer WILL be cooler than the air alongside the trailer, so the refer will have a better draw for cooling IMHO.
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato