This may sound like a dumb question, but we are looking into buying an automatice chicken door for our coop. Our current door opening is 11.5 x 11.5 inches. Our girls are not full sized yet, so have no problem getting in and out. I have Black Australorps, Easter Eggers, and a Swedish Flower Hen. The automatic coop door has an opening of 9 3/8 by 10.5. Is this large enough for full size birds?