Few questions about these heads. I generally put in hunter pgp heads and don't have much problem setting up the right stop on the head when the head is pressurized. That being said, Rainbirds rotors give me fits for setting the left stop when I am making adjustments after the system has been in the ground for a while. Half the time I can't turn the shaft to the left at all without spinning the whole body in the ground and it bugs the hell out of me. Am I missing something here? I have researched their instructions on the head and from what I am reading I can't figure out the err of my ways. Any advice?