I'm wanting to install two exterior nest boxes that the hens will be able to access from the inside of the coop, and that I can open from the exterior to gather eggs. I have a "chickens/ sq' space issue," and I am hoping this will free up the interior lay out just a bit. But, it's very important to me that the boxes are extremely weather tight. And I can't quite envision how to design & build them into the outer wall of the existing coop. Photos, words of wisdom, please?