Give them as much space as you can spare, but don't stress out too much. As they age, they move less and less. (Tip, have food at one end of their run and feed at the other end, otherwise they will literally lay in one spot stick their head in the feed and lean over and get a drink, seen it with my own eyes.) I get a couple bails of hay and as the run gets fouled up I ad a handlful to the bad spots to cover it and clean out the whole mess when they go to the processor. For my meat bird set up I use an old swing set frame covered in chicken wire. I did have a prblem with opposums last year, they were able to kill a couple birds, but did not get them out of the run. I will am going to double up the wire with welded wire this year.