Robi, what are you trying to accomplish? Are you saying that the "normal" trapeze system you got with the boat was not adjustable while on the wire and you are trying to figure out a simple way to make it adjustable without adding any parts?

Have you sailed the boat yet with the trapeze system set up in its "normal" configuration?

A new boat is kind of like moving into a new house -- you need to live with it awhile before you figure out how to best arrange the furniture and where to hang the pictures.