Hi Chris,
Are you planning to use the MOTU audio interface and the H9000 together from Logic? In that case, you'll need to create an aggregate audio device in Audio/MIDI Setup. Apple has some docs here: https://support.apple.com/en-us/HT202000
Using the H9000 USB interface can be tricky as the H9000 is always the clock master from the point of view of the computer (although the H9000 could itself be clocking off an external device or word clock), but the H9000 cannot enforce that the computer's sample rate matches its own. The practical upshot of this is that you have to select the sample rate on the H9000 first, then select it on the computer. For example, you might need to select the sample rate on the H9000 before opening your project in Logic.
For the I/O routing I've attached a screenshot of something that could work, although I haven't really tested it beyond checking that it can get 6 channels out of Logic and back in from the H9000. In my example I'm using channels 11-16 for the H9000.
Since, as you point out, there's no surround version of the I/O Plugin, and there doesn't seem to be a way to set the input or output of a surround track to an arbitrary group of channels on the interface, I created 4 busses to the outputs to the H9000 (stereo front, stereo rear, center and LFE) and added sends from the source track to these. Then I created 4 busses in the same way from the corresponding inputs from the H9000. I expect some care would be needed to set up all the panners correctly.
Happy to talk about this further over email or phone,
Best wishes,
Joe
