I got my second Synergy Syn-2 hooked up. The manual leaves something to be desired. I also got the switching setup, which the manual doesn't elaborate on much.
I think for hooking up a second Syn-2, the left hi/lo switch on the master Syn-2 should be set to lo. Otherwise it was really quiet when using the second Syn-2.
Edit: I have 4 OS modules currently loaded. 2 have been set to the "Marshall" setting on the cathode selector switch, while 1 is set to the "SLO" setting, and 1 is set to the "Fender" setting. It doesn't have a night and day effect, but is a bit of "seasoning" to the sound. I may set one with the "Fender" setting to the "SLO" setting if I experiment with it and don't care for it much.
Two are currently set to the "rock" setting, while the other two are on the "Jazz" setting. Have some of them with bright on, and one of them with deep on (with the Jazz setting). Various gain levels on the modules on channel 2. One is high gain (more OD Ratio/less OD Level, clean volume saturation), one is medium gain, one is high gain (slightly less than the other, more OD Level/less OD Ratio, only a little clean volume saturation), and the last one will likely be lower medium gain for a bluesier tone.
If I get bored, I always have a IICP to swap in that I am sometimes fond of and sometimes find a tad lackluster.