Its a lil complex, but certainly possible. I did it a long time ago on my R4/M3 Perfect combo, works the exact same on my new M3 Real/M3 Perfect.
I'm somewhat rusty on the process, it pretty much entails patching the rom on your slot-1, and putting a file on your slot-2 (and leaving a little bit of space on the slot-2 memory card).
Google Opera_M3.bdf and you should get some helpful results