We've had a down comforter for a while now, and we've used two different duvet covers with it. Both covers have been too big for the comforter. At first, I thought it was just a fluke or maybe that everyone's fits the same way, but now I'm starting to wonder. I just got a really cute (and really cheap!) duvet cover, but it's annoying me that the down comforter seems to swim in it. Any thoughts or ideas??