If anyone is interested in my take on hoop coop/tractors check out my gallery. It is made of EMT conduit, hardware cloth, 2 sheets on 1/2" plywood and some treated 2x4s
Sturdy and light enough to move by hand. I would recommend modifications for snow load if you wanted to use it year round. I housed 20-25 birds in each moved 2x daily in the summer
There are lots of photos and some of my plan sketches. I haven't yet done a full write up on it but a handy person could figure it out, including the homemade pipe bender.
https://www.backyardchickens.com/g/a/7050478/hoop-tractor/