I'm assuming that the standard 4' per bird is referring to floor space. I've just seen so many small, low roofed coops and they seem to have so little space inside, yet because they have the floor space they are able to accomodate X number of birds. I have a nice roomy 8x8' walk in coop with nice high ceilings. Doesn't the ceiling height count for anything? Even if I put up multiple roosts at various heights? It just seems like I should be able to accomodate more birds in my coop? It feels so much bigger than those reach-in coops.