I think I have now given up on both WAN and Flex for drip irrigation in the desert. The local watering guide suggests that you need about a 4 hour run time with 2 gal emitters on the drip system, and the flex schedule with xeroscape just won't let you adjust that high beyond just shy of 2 hours. I really still can't figure out what WAN is trying to do or what drives it.
It's a shame because it seems the system has a lot of promise,but not sure why these arbitrary limits on watering. It lets trees go longer, but not xeroscape which by definition often have very long run times.