Bill, thank you for the addendum - You are right in pointing out that
within the FAA 80%-200% limitation there may be a more restrictive
specification in a glider's POH. That's why, in many cases, private
glider owners carry their own weaklink to be sure the rope doesn't
exceed the manufacturer's requirement.

I also agree that a PT3 caused by a towline failure has a history of
bad endings.... better to be toward the higher side within the limits.

Bob