It might be better to just remove all the wall sheathing for a foot or so under the roof at the gable peaks and replace it with hardware cloth.
My little, Monitor Roof coop was never hotter than the outside even in midsummer.
I had a hardened run so I never closed the pop door.
I'm in NC too, in the Sandhills, and I think that you will probably need a lot more ventilation to prevent that coop from feeling like an oven. :(
The rule of thumb is supposed to be 1 square foot per chicken but placement matters -- heat has to be able to escape at the top.
Can you add a...