Just Figured this out yesterday. You will need to use both UC Surface (I use my IPAD for that) and Studio One.
In the UC surface
1) Link AUX Mix 1/2 into stereo pair if you want to have a stereo headphone mix.
2) Set the Level of the Instruments on the AUX Mix Faders.
3) Set the Dig Return Fader to ZERO
4) Set the Fader Levels on CH 17 and 18 to 3/4 up. (this will become apparent why in a bit). On and RM32 you might need to set the input to firewire (Not sure)
In Studio One
1) In a Song go to the I/O options page.
2) In the output section Create a new stereo output (Called headphone or whatever) Click the CUE mix Check box
3) Select CH17 and CH18 (This was the confusing part but it works like a charm.)
4) click okay
What this does is create a return back to the RM mixer that you can Route to the Physical AUX mix. The nice part of this is using other channels you can create up to 4 separate stereo or 8 mono. This biggest benefit was the ability to send the Click just to the headphones as it was driving me crazy in the control room.