Yes they do thump around up there... our house is Possum Central. It's quite an old house with about 100 points of entry and the owner is not interested in make it secure. It's one of the many things we have to put up with to live in a big house in a nice area. The owners don't mind us having pets either... you gotta take the good with the bad I guess. I have a chicken at my feet as I type too... it's like Noah's Ark around here!