I wanted to share my design for a mid-sized chicken tractor. It's approximately 8'x8' and houses 25-35 Cornish Rock crosses. Some changes I've made after I built it were to add a strip of fencing around the bottom that lays out on the ground and a 4' section of PVC gutter for fermented feed. Latest change is using a couple of cut up bicycles for the wheel assembly. Makes it easier to raise and move.
I'd be glad to email the PDF's to anyone who's interested