Thanks. That didn't work for me, but I found a strange work-around.
I you press alt+enter on Windows, it changes to windowed mode (same as adding "-screen-fullscreen 0" from that link you posted). Once in windowed mode, you can drag it onto the correct monitor, and then press alt+enter again to go back to fullscreen mode.
After you've done this once, the game automatically starts on that monitor from now on! :D