You might prefer to use just one model of rotor head for the entire project. Whichever Orbit rotor head is a copy of the Hunter PGP would be your best bet, because they have the best range of nozzles. I expect that's the Voyager, but confirm that, as I don't install Orbit.
Thanks for the tip; but I still need answers to the same questions irrespective of the rotor heads (i.e. Chart questions; GPM calculations vs chart; GPM vs. PSI for number of heads, etc.).