I've made some changes to my plan and it seems to be working out better than that.
Well, yes I carefully measured the property to begin with.
here's my backyard plan with some corrections. 1 square is 10 ft. Disregard numbers. I guess will be sticking with Hunters PGJ or Rainbird 3500. Haven't decided yet.
By the way I found pretty cool software Pro Contractor Studio. You can download demo version. You can draw your plan,. It has database of all sprinklers with specs. In there you can check water distribution. I checked my design and it looks good. At least in an ideal world. I shall see the real world performance