I have a 4x8 now. It was fine for my 7 hens and 1 rooster until I put ducks in there as well. Now the chickens free range, the ducks use the run during the day and they all stay in the coop at night along with the goose. I can't find free range eggs and step in free range poo every day. So I need a new coop. I was thinking 8x8 and on wheels so I can move it easily if needed in the future. Problems with old coop are that the 2x4 space for feed area doesn't function as well as I had hoped. Snakes enter the coop occasionally (and tried to eat a chick) and attempt to take eggs. I don't think I can stop snakes but I think 4 x8 space for one feed can and new chicks or hurt chickens in a small portion of that with hardware cloth to keep snakes from chicks and the rest of space for 2 nesting boxes accessible from outside and two windows lined with hardware cloth for air flow in summer. Not a tractor per say but kind of similar to a chicken trailer...I need to be able to move it because I can't decide where it would be best to put it. Inside a fenced area with my dairy goats and barn where they could potentially free range confined within the goat pasture (and poop where my milk goats lay) or over next to ducks with the ability to make small run and later enclose more and let ducks/chickens range together during the day in larger run. I don't think they will fly over 4 ft fence. They normally don't otherwise they would be in the goat pen occasionally now by flying over their fence.