I know if you put a flat top on them then they'll get pooped and roosted on but does it make a difference if you put an angled top or no top at all on? Do they lay better one way or the other?
I didn't have a top on mine at first and while they still laid, I found they seemed cranky with one another, once I rebuilt them a community nesting box, which was deep and had a top, they were much happier and less likely to march back and forth in front of the nesting box preventing everyone else from going in. a top would be beneficial, especially in winter