Something else to think about: It is best practice to actually overlap maximum of 80% of the sprinklers coverage radius instead of 100% since the mfg. figures are usually for optimal conditions, ie. no wind, perfect water pressure, perfect nozzle angle, etc.
Hunter I-20s have specific nozzles for different throws, do NOT use the screw to reduce the radius, that is not what it is for and as Sprinklerman pointed out, there should be MPR nozzles for Full, Three Quarter, Half, Third, Quarter. Those need to be put into the appropriate locations.