I'd like to do some realistic sky images that do not have either a ground OR that white cloud layer that persists even after you uncheck "enable ground" but I can't figure out how to do it.

Essentially, I want the sky to keep going "down" without hitting that cloud "floor."

If you're not sure what I mean, set up a pic with realistic sky and uncheck "enable ground" and you'll see that there's still, essentially, a ground.
I want empty space.
Does anyone know how to get rid of that?