I have a neighbor who has a small 5th wheel trailer, and talking to him some time back and he said he also had problems with mud wasps. I have covered all my openings with plastic bags. On the ac unit, bought a mattress set a while back, and used a plastic bag they came in to cover it, using a eight foot stepladder. But these wasps have a way of getting into the smallest places. Oh well guess we cant have it all. Along with the sun, some rain must fall.