silkie advise pls

hi ive found a guy whos quite local with a variety of colours. there not quite ready yet so were going to prepare a coup and space for them. v exciting! ive been doing some research on the breed on the net and have read they cant fly is it true, as i was thinking of getting 4ft posts to attach the wire too, or do you think i could get away with lower posts, or would we need higher ones, im prob going to go and get the posts tommorow so we can get cracking with it, any advise welcome pls    

They can just about get off the ground and fly above it for a few feet if they see food coming, it's the only time mine make any effort.