Yes on both Mac and Windows.
Set Sigma to use the Logic (MCU) profile.
In Reaper Preferences add a Mackie Control Universal set to use the first Sigma ipMIDI port (channel 1-8) as defined in the Sigma browser > press OK.
Now add a Mackie Control Extender in Reaper set to use the second ipMID port (channels 9-16).
Before closing this window, set the value of the Mackie Control Extender Surface Offset (tracks) to 8 > press OK.
Press OK again to close the Reaper Control Surfaces preference window.
Note that ipMIDI should be configured with Loopback = OFF.
On Windows this can be configured by navigating to Start Menu>All Programs>ipMIDI>ipMIDI Monitor.
On Mac OS, navigate to Applications>Utilities>AudioMIDI Setup, then Window>Show MIDI Window. Double click the ipMIDI icon to edit the Loopback state.