Thanks for all your comments and suggestions. We'll put more ventilation along the tops -- about 250mm (5") deep and they will all have shutters at the tops for when the rain blows in sideways. Eventually we'll put in a run which will be easier here because of not so many predators, and we'll lower the height by about 200mm (4"). My husband said he'll only hit his head once and maybe we'll put a soft bumper above the door on the inside for when we forget we had to lean in to clean the coop.