Do any of you use sand in your run? I'm seriously thinking about putting 3-4 inches in the run as the dirt turns to this horrible smelly mud when it rains. From what I'm reading, people seem to like sand in the run and in a poop board (I'm using that and it's sooo easy to clean) but not so much on the floor of the coop as it stays too cold in the winter. What do you guys think?