Output for one mono reference monitor

Hi!
I’ve been using the Qu-Pac “Alt Out” output for stereo monitoring for a few years, as I can control its volume directly from the front panel.
Now I would also like to add one mono reference monitor but from which output and how can I get the summing of the master channel to mono?
Thanks!

Do you have a stage box with the QU Pac, you could assign one of those outputs to be L+R.
You could use a post fade mono mix out with all the channel send levels set at the same level.

You could build a mono summing adapter like this and use it on a stereo output.
https://www.ranecommercial.com/legacy/note109.html

I don’t have a stage box. Actually can I use mono outputs on the back of Qu-Pac for this? These are not used currently.
Can I route master L & R being summed up into one mono output?

Yea, cable option is also one option. But I think it’s not the best option, because I can’t solder, I need then already finished product.
Thanks!