After years of white knuckle sheet holding, I conceived this reefing method. It works great. An added benefit is that it reduces not only sail area but also weight aloft because the gunter yard is 2 feet lower on the mast when reefed.

The hooks I used were hardware store rope hooks. I had to bend them slightly. You can probably find something similar in stainless at a marine store.

This assumes the original small gunter or Mk I main. The method can be adapted to the later quadrilateral sail but will require a couple of additional changes, easily made.