We are currently using this chicken tractor for our four birds (2 RIR and 2 Gold Sex Links). We are moving it every other day to keep the grass alive and give them access to new bugs and such. They seem really happy, however I am toying with the idea of creating an supplemental/portable run that I can hookup to the tractor door to give them more room for foraging. Does anyone have any recommendations on what materials to use to build this so it is light enough to move but wont fall apart? Links to designs or examples would be great. Thanks!