My earlier post I said 12''. I will eat crow. We tried to keep it between 12 min and 13 max depending on how all the other pipes worked with the layout. It was routine to start layout from the bathrooms out. The plumbers pipe layout trumped all others unless they really screwed up bad.13 to center on rough.
I could never figure out why the plumbers never backcharged us when we put a screw in a pipe either. :whistling