sizing circs in manifold job

Bob_36

I would like to know, when sizing circs, do you just consider the longest run from the manifold to the rad(ci) and back or add all the runs to all rads off the manifold? They will be home runs. This question is for figuring gpm as well as ft of head. I am running 1/2" and feel 007 is more than I need. Thanks for any help.