300lb (130kg) pilot

Interesting comments from Bruce. Just be aware that any time you exceed the numbers in the aircraft manual, YOU are now a test pilot and risk taker.
Providing rides to the general (unknowing) public, and anything happens causing injury, an unlatched canopy, hard landing, rope break into the trees or rocks, and you have just introduced yourself and your club to a world of liability issues. Same goes with students, who are relying on the experience and knowledge of their instructors.

I agree with you logic on flying to reduced G loads or Vne, but I do not agree with the practice.

This will not happen in my club. I am at 210# and know the max weight of any student or passenger I can take in any glider I fly.
We live in a very sue happy environment now. Why ask for a problem you cannot defend.
BillT