Rainbird 1800-PRS heads already have internal 30 psi regulators. You must have really high pressure (or defective regulators in the heads) for the adjustment to make a difference. Usually, anything under 75 psi is normal for those heads.
The water pressure is high coming into the house. It is in the range of 80-85PSI and I don't complain about the high water pressure. I am sure that the double check valve and piping have cut this back a bit. Maybe the pressure at the heads is close to their max? I haven't checked this yet and will try to attach a gauge to the last head connection on the zone to see what the pressure really is.
I did turn the valve's flow control down to 50% (about 4 turns fully open then back 2 turns) and this made a difference.
