Hi Elliot. Welcome to the Opto 22 forums!
Sounds very straight forward.
1 thing you will need to do and 1 thing to think about.
First, you will need put each RIO’s certificate into the other one so you can talk back and forth.
We have a forum post on how to do that here:
Once that is done the thing you will need to think about is if you are going to have a master / slave sort of setup, where one RIO runs the main flow and simply talks over the network to the other RIO, or if you want a sort of hybrid setup where each RIO is doing their own thing in their flows and talking to the other as needed.
If you are going to go with the latter, then you need to be super careful that the two flows don’t both write to the same output with different commands, ie RIO 1 telling DO1 to turn off and RIO 2 telling DO1 to turn on. Chaos will quickly follow. And do note, this is a problem to be solved in all control systems where you have two programs running - be it a human interface or a system like you have.
Feel free to go over the pros and cons with each option or ask any questions you have as you go along, as you can probably tell we are big Node-RED fans and love our little RIOs.