I use 2x4's inside my coop with the 4 side up. I dont think it really matters if you dont get to cold of weather but i like to have the 4 just incase. You never know what could happen. And the who chickens need so much room per chicken. well i have 3 roost bars all at the same height and they are 4 feet long with only 11 chickens and 2 are silkies and 2 are leghorns. So thats alot of roost. and i find they dont even use half it. They like to huddle all together so just make sure you have room so it looks like a few more can be put up there and you should be good.