Hey!
I've never done this myself, but recently when I was researching for multimonitor options, I've found out this:
-mon number P A7.20
In a multi monitor systen, uses the monitor with the given number (1,2,3,...) for fullscreen display, instead of the primary monitor. For using several monitors at the same time, start the main application in server mode (-sv, see below) and start one client application per monitor (-cl -mon).
It's related to the command line, search manual for 'Command line options' (in offline manual you can find it under 'Starting the Engine' section).
Best regards.
