You are very wise to have gone big. I predict you will have 20 chickens a year from now. We are new to keeping chickens and went with a smaller coop so we have no room to expand. Right now it does not matter as our township ordinance limits us to 6 chickens. While we would love to move out of the suburbs I don't think we are going to. So our coop should be adequate. But it does seem the more space you have the less behavior and disease types of problems you can expect. or at least that is my opinion based on all of the research i have done.
I do wonder if the best ventilation would be some gable vents ....
something like this
View attachment 2893697
Better to open the entire gable triangle, cover it with hardware cloth, then install either a roof extension or an awning.
Those louvered covers generally only provide square inches when ventilation needs to be measured in square feet.