They are chained via firewire as well as spdif for monitoring.
If you just want to use just the 2 mr’s then yes connect them via adat and direct analog channels to digital channels, then you can monitor all 16 channels from any output.
I however have other adat devices, so I connect the adat to the other devices and pass the monitoring over spdif. I can only monitor two channels that way if I use direct monitoring, but I find lately I haven’t been using direct monitoring, I’ve been monitoring through cubase, which gives me a lot of options using the control room.
This gives me a total of 28 channels (I lose 4 for monitoring via spdif) which is what I need for recording a group all at once, and I find it handy to just leave all the instruments with their own dedicated channels so I don’t have to reconfigure when I want to record something.
There’s a lot of ways to set this up, this is just how I find it works for me. Lately I’ve been thinking that a small external mixer would be good, I would plug 2 outs from each mr, and then the speakers into the mixer, this way I wouldn’t lose the 4 channels for the spdif, and I could use direct monitoring if I wanted. Just kicking that one around.