Yes, this is possible since the introduction of the special Master/Slave feature for the RM mixers (not to mix with the stagebox modes of SL/RM). The RM at FOH needs to be the Master. But...

It does not work without a network (router). The via FireWire connected computer "sees" channels 33 to 64 only via WLAN, which applies to UC Surface as well as Capture. 64 channels (+ 4 tracks in Capture) looks quite impressive, and there are two ways to use them:

1) as one single 64 channel mixer,
2) as two coupled 32 channel mixers.

In both cases you see only one "virtual" mixer in UC Surface, which makes sense for 1), but not really for 2). Two 32 channel mixers is exactly the stage/FOH scenario (live, studio, church...), with the Master at FOH, delivering all FireWire functionality including Smaart. Main l/r and mono and Mix Outs 1 to 16 are merged (identical outputs at both mixers = merged outputs). And then comes the trick: The Slave (RM on stage) sends its inputs to channels 33 to 64 of the "big" mixer. To route them to channels 1 to 32 simply select "network" as source of channels 1 to 32. Now you see both sections working simultaneously.

IMPORTANT!!! Latest at this point you need to get channels 33 to 64 out of the audio routing! You will hear some latency if channels can be heard "double". You simply need to unselect the routing "Main" and "Mono" of channels 33 to 64 and use the faders and routing of channels 1 to 32.

As you might guess this opens some more possibilities. You might want to use channels 33 to 64 solely for monitoring or special mixes or delay lines with a different processing. But you need to remember that the 4 FX machines are also merged. Otherwise you can see this as a 32 channels/tracks system with split channels/tracks.

You need to use the AVB switch at FOH/Master because of the AVB ports. The CS18AI works just fine in this kind of setting. You work with channels 1 to 32 on fader banks A and B and control the inputs (gains) in channels 33 to 64 (fader banks C + D). And you can use CS' on board buttons to control Capture. Capture automatically shows up in UCNET under "Software Control" (right part of display).

So get the second RM! It will make everything work! Actually a RM16AI does all that as well, but a RM32AI is more luxury...

Thanks for your info. I'd like to explore the one single 64 channel mixer option a bit further. If I declare Stage end as Master then channels 1 to 32 start there. Presonus advise that all Main and Aux outs are mirrored so I'd get those at both ends. However they imply that Firewire can still come from Slave in Control Room. Is it your understanding that in the 'one single' 64 channel config, Capture will 'see all inputs'? There's some doubt about whether Line In at slave end would work, but no problem if you have 64 channels of which 32 are at the FOH/Control Room end - I'll just DI it. We have some mic inputs coming in to Control Room end of things (wild mic and radio systems). I'm not fussed about the channel assignments (can use filter DCAs to make that manageable) as long as everything else works more or less as I've described. is there a gotcha?