If you wanted to do poop boards you could do something like this. You can even put more roost over the nesting boxes.
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Palquire - if you do use this design, I'd think about shifting the nest boxes under the poop board. If room, could either do a dusting box or hang feed here as well.
I use open air coops/run combos & tractors due to heat/humidity here in NC, so I'm not familiar w/ having a closed coop. But, when hurricanes have gone through, I've often combined flocks (moving grow outs from tractors that might not survive the storms into the more solid pens/coops). This has put way too many chickens in 8x8, 8x12 & 8x16 coop/run combos - the results have caused feather pulling, hens killing hens by cornering & pecking to death & roosters who died of either heat stroke or heart attacks after fighting till couldn't stand anymore (no physical injuries). Not fun & not pretty.
I can't imagine having birds constantly cooped during blizzards or extreme cold (though we cared for horses & ponies in MT & 96/97, we were buried in a March & then April blizzards near the Canadian border).
So, my recommendation is following others' ideas in the area you live and go as big as you can for your birds.
You might also check out Alaskan's coop info & articles. They are interesting!!