i will have a total of 12-16 chickens, they have a huge run that is 20' by 14' and i want to make a folding tractor so they can focuse on the part of the yard that needs help instead of them just roaming around. how big should it be? they wont be in it all the time, or is that too many chickens in a small space? i guess i could always just put half or so in hafl the day then the other half in the other part of the day.