I have a tractor that is 4 x 10, and I think that size works well for 3 or 4. The coop part is 3x 4.
The coop part is way too small to have feed and water up there, so I put those in the run area. Make sure there is easy access to the feed and water, and that they can be kept dry.
I do not...
I found it safest to have a flexible wire apron than could be weighed down with a few rocks... if the coop is sitting in a not fully flat spot.
Make it strong enoug for a dog to bag and jump against it.
Also, you need quality wire, securely attached with tiny holes...the problem with a tractor...