I am trying to figure out how to add wheels to my chicken tractor, which is constructed of 1x2 lumber. The way my yard is set up, I would ideally like to have "castors" so that I can easily swivel the coop into corners. Simple wheels that go back and forth are not really right here. If I put the castors (or wheels) under the main frame of the coop, then the coop bottom lifts off the ground - allowing chickens out. I'd love to have 6" castor wheels. Any ideas?