Chicken tractor size?

[i like birds]

Hello all I have 12 birds and need advice on chicken tractor size. I don't want to crowd my birds but am concerned about making a tractor that is hard to move because my yard is all sloped. I even considered making two seperate units but am using sracp wood and also am concerned about two times the maintenance. Thank you in advance.

 

[my sunwolf]

Are they full sized hens you are talking about? If so, the minimum is 4 sq ft each, but the ideal is 10 sq ft each. We have kept docile hens in tractors with 8 sq ft each and they have been very happy. Anything smaller than that and even the sweetest of hens can get aggressive with each other. You also make them more susceptible to respiratory disease and other illnesses by crowding them together.