Not to hijack the thread but I have almost the same question. Note I have read your document here on impact of measuring one leg of split phase.
I think I’m going to mount the two units in different boxes, and each with their own power outlet. I also noted in another thread here the statement to ensure if you split a reference source you maintain polarity. So I think I already know the answer but…
Is there any advantage to (and technique to allow) one to use the two reference sources to be more accurate by measuring each leg independently?
Or just stick with “use the same leg for each reference source” in which case I’ll run one branch circuit to both boxes.
In my case I’m going to have to references anyway (not split), just trying to see if I can glean any additional info from doing so.