From research I have done, I didn't think there was any config for dual/single zone in the FDIM. The zone info is in 2 places (HIM, which is configurable to single/dual via Forscan), and the
ICC button board that connects to the FDIM. The front panel buttons are different for single/dual zone, so I figured that it was just a matter of plugging in the correct front panel.
Which half byte was different between the two?