Print to PostScript Quark 6

I am trying to print separated Quark 6 PostScript files without success…the following code:
set desktopPath to (path to desktop) as text
tell application “QuarkXPress”
tell document 1
set docName to name
tell print setup
set printer type to “PantherPro62”
set resolution to “1200”
set halftone screen to “100”
set separation to false
set paper offset to 0
set page gap to 0
set data format to binary data
set registration marks to off
set paper width to “12.583"”
set page position to center horizontal
set print colors to composite CMYK
end tell
end tell
print page 1 of document 1 PostScript file (desktopPath & docName & “.ps”)
end tell

will print a composite PostScript file to my OS X desktop…when I change the line

		set separation to false


		set separation to true

I end up getting a zero byte length PostScript file on my desktop. Anyone with any ideas on what I am doing wrong? Thanks.