Your coop looks DYNAMITE BEAUTIFUL,,,I measured some things today. My roost diameter is 3" for the top roost - the one they sleep on - and 2.5" for the intermediate roost, the one they use to jump to and from to get up to the top roost. And the distance between the floor and the nesting box openings is 1 foot from the floor itself, and 8" from the top of the pine shavings. Because the nesting box has round openings which are several inches higher than the floor of the box inside, it's hard for the hay that's inside to be kicked out, or for shavings from the coop floor to be kicked in. Here's what my nesting box setup looks like:
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