Yeah, unfortunately, it does sound like it will be a bit too small. The Orpingtons would definitely appreciate a larger opening!I’m not really sure. I got a batch of 10 mixed brown egg layers. I think they are Sapphire gems, cinnamon queens, black sex links and buff Orpington. That’s my guess based on no experience. I do think 9” will be too short. I think the automatic door I ordered is too short.