I just have 3 hens for now, but I'll be adding a few more. So far I am totally in love with my langshan, so I expect that the majority of my birds will be on the larger end. I'm building a community style nesting box and wanted to cut an egg-shaped hole in the front as an entrance. What dimensions are going to be large enough for the girls to get inside without being so big that it looks/feels open/not cozy?