Mono mix for delay speakers.

On my other desks I would simply route the LR mains to a mono matrix and then to an output port.

Any suggestions on a work around while we wait for a mono matrix?

Thanks

using one side of a stereo matrix

Unfortunately this won’t work. I have tested this scenario:
USB-Player sends on a stereo Channel, which is fully panned to left, to the LR Main. Width of that channel is Mono.
So I can see that on the Main bus on the left side a signal is received.
Now I send the Main Signal to Matrix 1.
I connect a Box on on the right output of Matrix 1.
No Sound. I also tried to play around with the pan of the matrix send on the Main. No changes.
So when there is a hard panned signal in the stereo sum of main you won’t get that to the matrix.
I see at the moment the only chance to use a Bus, either a Aux or a mono group, and send all signals to that group and use the bus output for the delay line. the group would be the easiest because it will follow the faders for the main bus.
A mono matrix would be really helpful in future;-)