For what it's worth...
Spoke to a few "engineers" at a mfg about a similar situation.
First comment was "180 va each"
Second comment was "6 on a 15"; "8 on a 20".
Third was "read the enclosed literature".
I wasn't thrilled at any of the above answers and handed the instructions to the guy who asked the question.
Personally, we keep it "in sight" and no more than two downstream duplexes.
John
