Yes you can indeed cascade the 168RC.

    1. Connect a MIDI cable to the 1st 168's MIDI IN to the 2nd 168's
    MIDI OUT. In the same way connect the 1st 168's MIDI OUT to the
    2nd 168's MIDI IN.

    2. Sync Adat's together

    3. Connect the optical output of each adat to the IN-A of the
    respective 168's.

    4. In the 168's MISC mode set CLK source to "INTERNAL".
    if the adat is an XT or newer set the adat's CLOCK SOURCE to
    DIG 48K.

    5. In the 168's MIDI mode, set System Extension to "Cascade
    Master" for the 1st 168, and to "Cascade Sender" for the 2nd.

    6. On the 2nd 168, assign Master L/R or Solo L/R etc. to the Dig-
    Out-B in the EX.BUS IO mode. for the EX. BUS IO mode Input Sel.
    on the 1st 168, input the Master L/R or Solo L/R etc. that was
    assigned to DIG-Out B on the 2nd 168 into the same bus.

It's very cool. You will no longer have 32 lightpipe inputs. You could then use a Midiman Digipath for some creative patching.  This cascade setup is not intended to give  you more digital inputs per-say it's a way to have 8 more analog inputs, plus it allows you to solo channels on either Korg and it will mute all un-soloed channels. There are work-arounds that you can do, but that might not be your goal. I use 2 Korgs not  cascaded that can be routed to either my Adat's or Dakota/Montana  thru a Digipatch and it seems to give me the flexibility that I  need. This console can do alot with some creative patching and imagination. Dive into the manual and go for it!

Chris