Try the -multimonitor command-line parameter (add it to your current parameters).
I believe that is the name of it... might be -multiplemonitor. In fact, either may work. In any case, it will fail to startup if the name is incorrect, in which case you should try the other one.
It's -multiplemonitors, it works perfectly and it's fully documented.
I have slapped myself hard on both wrists and apologise to you and everyone else for wasting their time.
Regards, Cliff.
