How many more of those we need till we conclude that the rudder
waggle does NOT work?

I think this is a reasonably valid point. There HAVE been a number of
people who have misunderstood this signal.

Perhaps something else would be better. The question is what signal
would be a good replacement. You could have flashing lights on the
towplane, perhaps mounted just above the towhitch. The only thing is
you'd probably have to install two lights. Say one yellow and one red.

Yellow means you've got a problem, but if you can get it fixed pretty
quick we'll keep going. Red means get off now or I'm gonna dump you.

If you don't have two signals, I'd bet that we'd still have people
releasing when they didn't have to.

As I think about it, it might be best if there was a single array of
high output LEDs. When both "colors" of the array are "on" then you
have a single visible color that means "ok" (red and blue make green in
concept, but in emitted light that combination doesn't work). That way
the glider pilot can verify at the start that both signals "work" and
they stay "on" for the duration of the tow. If either the "warning" or
"get off" switches are selected in the cockpit then only the
corresponding "color" is then visible to the glider pilot. Perhaps with
the "warning" being a steady signal and "get off" being a rapid flash to
help with fast recognition and a sense of urgency.

Other thoughts?