Gramma - My favorite spreading evergreen is Broadmoor Juniper. They would meet all your criteria except that they may get 8-12" high in the center as they get older. Other shorter spreading junipers that I have tried do not hold up well with age. I love their slightly bluish-green color, they don't open up in the center and get "ratty" looking and they drape beautifully. A couple years ago I planted one among the rocks around our pond in partial sun and it is gorgeous. Some nurseries catalogs say that it gets to 30" tall, but that isn't the case with any of mine that are around 10 years old.