[cycler]

Works perfectly! For future reference, Unity wants to show it's launcher on the first monitor. So the order of TwinViewXineramaInfoOverride is important if that matters to you. I wanted to show it on my largest display so....

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "1"
    Option         "TwinViewXineramaInfoOverride" "2560x1600+640+1024, 1280x1024+0+0, 1280x1024+1280+0, 1280x1024+2560+0"
    Option         "TwinViewXineramaInfoOrder" "DFP-1, DFP-0"
    Option         "metamodes" "DFP-0: 3840x1024 +0+0, DFP-1: nvidia-auto-select +640+1024"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Thanks much!!