How to make the main tray the default output

[AB1984]

On our KM c8000 Command Workstation (when set to 'Auto' output tray) always sends jobs to the stapler sub tray, regardless of size or anything else, is there any way, without setting it for every job, to make the Main try the default (or Auto) tray. All our engineers seem to be at a loss, and after having a look round I have no idea how to change it.
We're using CW 5.3.1.32.

Thanks in advance