On this particular issue I don't believe Ralph's book will help. It was written a long time ago, and he bred mainly Barred and White Plymouth Rocks. You are correct about the willow colored shanks. These birds should not be used for breeding, as willow should be treated as a D.Q. for showing, and your hen would pass on the yellow epidermis gene to 100% of her offspring. Since it is a recessive, her offspring would not show it unless they also inherited the same gene from their sire, but they would be carriers and keep on passing it to their chicks.