So couple more quick thoughts here:

1) Make sure both 11R's are set to 96K... otherwise the "slave" 11R will show lots of digital aliasing in your tone

2) Haven't tried it yet, but if you want to simplify the setup you could run an Amp Out without cab to the Guitar Input on the secondary 11R, and then just set up the second 11R to have a cabinet and post FX instead of a full rig

3) Sounds awesome and huge if you set up different mics on each unit and different reverb amounts on each either. In particular I recommend using a bright mic on-axis on the first 11R with little to no reverb, then a dark mic off-axis on the second 11R with moderate reverb. This also means you can take the Steve Albini approach of "EQ"ing your tone by adjusting the levels between the two mics/units

4) I got my second 11R for $150. That is absolutely bonkers. I suspect that with this setup I'm close to Axe-Fx in terms of tone and feel... and in theory you could put this all together for $300 total. Its an absurd bang for the buck and means that even a very frugal guitarist can get a hugely flexible rig with separate stereo channels for not much dough, with inherent backup should one fail, and the ability to serve up ready tones to a second guitarist or bassist at home or on the road. Insane.