Hey, I see the new pics here on this post. Cool, now we can aid in what you need...
This is what I'd do with that set up. You've got a great coop there and one of the best features is it will physically vent better than a box. 
Hoping it's all screwed together so easy to adjust. On your eve ends make 1 to 2 inches of space. That means to raise the roof over the 2x6 (or 2x8) that is side wall. Yup, just raise the roof and provide a full 1 inch space on each eve wall. Then cut out a triangle of each gable end. With that slope your very efficient air circulation. It takes much less (physics proven) to naturally move air in and out with that slope.
Basically with a full inch on each eave the entire length (as in raise the roof or replace the eve end top board  from 2x8 to a 2x6) then give 1.25 square inches per gable per chicken and the flow will almost put out a lit match. The air flow and circulation of air in your coop is optimized for that closed coop.
Say ya got 6 chickens then with that inch of raised roof the triangle of gable end needs to be cut...oh let's go 4 inches to be conservative. And I'm saying from peak down 4 inches measure. It isn't much and will change your chickens world.