The sky and the horizon are infinate. They cannot themselves be independantly moved. What I have suggested is not so much a 'work-around', more of a 'the only way to do it' .

Try this:
Load up a new page in Bryce
Select DIRECTORS VIEW
Drop the groundplane to  y = -500 (y equals minus 500)
Rotate the main trackball by pushing it up
The Horizon line should drop to the bottom of the screen.
Repeat this until the horizon vanishes entirely.
You should be left with just the sky.

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All the Woes of a World by Jonathan Icknield aka The Bryster

And in my final hours - I would cling rather to the tattooed hand of kindness - than the unblemished hand of hate...