I have recently cabled up a black ADAT, 2408 and 168RC and I am still in the flat part of the learning curve. I am using ADAT light pipe sync, and so far that seems to work pretty well. I have noticed some faint clicks when monitoring the digital master output (channels B1/B2) of the 168RC when monitoring on the 2408 but these seem to disappear (or at least diminish below what I can hear) if I switch the master output to B7/B8). I also do not hear the glitches when monitoring the 168RC directly, so I am wondering if I have a defect cable.
I plan to try cabling up the wordclock sync soon and I will let you know how it goes.