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?

Use these two to lower and then tilt back inside your printing frame.

Brian

bwtr

Not sure I follow you. Could you explain a bit more indepth? 

I think that Brian says to you point your camera up.

Follow me at euQfiz Digital

I guess the end result is the same as Camera movement but I am suggesting a different approach.

I am saying Lower the Scene and Tilt it back with those two tools.

Brian
(Image results posted on the Daz thread)

bwtr

I think that above folks have the best solution.  Unfortunately, the only way to really lower the horizon is in the sky mode (Mark, you may want to step in here if I'm full of hooey) even though both mode show the Horizon Altitude that you can plug  say -22 inches, it works in the sky mode but I can't get it to do squat in the realistic sky mode (yeah, if I lower the puppy to  -3000, I get the Earth's curvature-a nice grey curved surface-at least in Carrara 5 Pro).  Jan

Yep, the way Brian explains it is the way i do it if i want to render just a sky background. You can get something like this, and if you adjust your production frame, you can get a sky in portrait aspect ratio.