I've come to the opinion that most chicken tractors are only appropriate for about two chickens. Just too small for many chickens for more than about 4-8 hours in any one location. Any of the bigger ones are also going to be limited to the locations they can move through in a small landscape.
I now use mobile perches and mobile nest boxes that I can move around and I use the easily movable plastic fencing and step in stakes to give the chickens larger areas of yard so I don't have to be around to move the "tractor" several times a day.
Now I might sing a different tune when/if we start having troubles with predators but I have a feeling my choice then will be to see about getting a dog that would protect the birds but I haven't done much research on that yet.
Thank you so much for posting, i am not yet a chicken owner but giving thought to what might function on uneven terrain if free ranging during the day does not pan out on our farm as we will have chickens within a month. There is always something positive to inspire thought on this website!