Using MLAT port for local only display

What is the data format for the port that MLAT feeds to dump1090-mut for local display only?
My interest is to have two dump1090 systems which both feed FA.
I would like one of the dump1090 systems to display traffic from both systems. The unit receiving the additional traffic would be considered the “main” system.
I don’t want the “main” system to send the data is receives from the secondary dump1090 system to FA. That could cause MLAT issues.

Real world example…
The point of this is, I have one system which is for 978 UAT. I would like it to feed FA as a separate site. (It’s easier to track the stats).
I have a system for 1090ES which also feeds FA and receives MLAT in return.
I would like the UAT system to forward what it receives to FA (as normal through piaware), but also forward it to the 1090ES system.
However, I don’t want the 1090ES system to re-forward that UAT data to FA twice.
My thought would be to have the UAT data send to the same port on the 1090ES machine which receives the MLAT data. Can this be done?

This would also be useful if you have a couple remote 1090ES systems which feed FA, but you would also like to have all the data displayed on a single dump1090-mut system.
IF it can be done. So, thoughts?

If you configure it for “beast” output (the default setup has beast-format output going to localhost:30004) then that’s in the binary Beast format; dump1090 by default will accept input in that format on 30004 and generate output in that format on 30005.

For your setup I think you need a separate --net-only dump1090 that does nothing but accept data from other systems for display, and does not forward that data on anywhere else. You can then point all of UAT, 1090ES, and mlat at it.

Ok, that makes sense. Too bad one install can’t be both. Is it reasonably possible to run two installs of Dump on one system - one standard and one net only?
An issue of renaming/duplicating configs, etc?