Just picking up on this - as per your original post.
Unfortunately, I've been nowhere near an Expression desk recently, but think I may have solved the issue.
Originally you said you wanted to duplicate the Left/Right mix outputs onto other outputs (in addition to the standard channels 15/16).
To do this:
In the main menu Select 'Outputs'
Select the Main Output channel fader (button above the fader).
You should then see this menu:
Click on the cell to the right of 'Patch 02'.
Then select an (odd-numbered) output, e.g. 'O/P 13'
The main mix will now be duplicated on channels 13 and 14.
I haven't actually done this much, and can't validate this action, so I'm just going off the manual - hope it works!