We're building a coup that's quite small, about 10 sq. ft. and only 3 ft. of interior height. I know the perch should be about 16 - 18 inches above the floor and should also be noticeably higher than the nest box, which brings me to this question.... Must I actually use an enclosed box for the nest, or can it just be something like a pan with no lid? If it must be a lidded box can it be rather short like 12"? Or, if I make it taller with a slanted lid would that be acceptable, say 16" at the back and 12" in the front? Whatever I end up with, it will be sitting on the floor. Thanks for your help!