The biggest problem with any screen if air flow restriction. I can't tell if these are deep enough to overcome the flow restriction. I use a something like that over my furnace
exhaust and intake ports, but I know there enough space so that there's no flow restriction. The air flow for the fridge
venting is marginal at best and reducing it more could cause some serious problems.
I use a bug stray that supposed to be good for 90 days, I spray the fridge vents about once a month. I had spiders get and build a nest on the propane
I was concerned about wasps getting into the furnace
and building nests on the fan. So far nothing has happened there.
FYI I also keep the fridge running all the time, electricity when the trailer's at home and propane