RE: 150 meter rule.
We did this 20 years ago and it was an interesting experiment. We put a person in the field right at the 150 meter pole. The instruction was to just watch the airplane. If the airplane is closer than 150 meters the persone in the field will be facing the flight line. If it's father out he will be facing away from the flight line. If you are on you will be looking at his side. This way there is no signaling. All your caller has to do is watch which way the person if facing. Most of the time, even when you thought you were close you were looking at the back of the persons head.