So I am a biologist, artist and nurturer, but I am not an engineer or physicist which is why I have put off figuring out the wheels until last minute for my tractor. It is 5'x3' with a coop built out of plywood on a frame of 2x3s. The pen is underneath, with 2' tall space covered with hardware cloth. I don't have photos of it yet, but here are my early plans. I will try to take a picture tomorrow. I was thinking flip under wheels, but this sucker is heavy now that we have it built. I was wondering if anyone has had luck using skis for pulling tractors around, or if anyone has other suggestions on how to get this thing moving.