When you put on the run... will you extend that roof at all over the run?
I know the Dakotas get cold and windy, but I can't remember how much snow you get.
If you extend the roof over the run, a
nice huge vent under that run roof would be great, like maybe a hole 2 feet tall by almost the entire 8 feet wide. You could keep the siding you cut off to close the hole to only 1 foot tall or 6 inches tall when it gets way below zero.
But... depending on your wind.... you might want to keep covers on hand for all of the holes you cut... then stand there in the coop once a horrid winter snow storm hits and play a bit....
You do NOT want to cover up all of the holes, ever.
But... sometimes it is hard to figure out how that wind will swirl about until it IS swirling about.
I started with my eves open, and the wind here just swirled right in bringing snow with it. But... my 6 inch tall gap all along 2 and a half sides of my shed, located directly below the perches, works fine.

What can I say.