does it matter left or right when running to single active CLR cab?

Nah, just set the output to Master Mono.

Lucky dog Give us your review when you get a chance.

I'm on the waiting list, hopefully my name comes up in the next few weeks. Then I plan on buying a second one around February.

Couldn't you also just use the monitor output which is always mono? Or would that sound different?

Monitor output can also be stereo, depending on the settings in the output/master menu.
And no, monitor output doesn't sound different to main IF there are no different output EQ settings.