I'm toying with the idea of a small cleat on the center portion of the trapeze handle, to which you could quickly tie the chicken line once you're set on the hull. Then, you'd only have one connection to the sailor - the standard trapeze hoop.

Only drawback I see so far is that this cleat could go flying at your face if you are on the trampoline and the thing comes snapping back at you (if your crew drops out of it, for instance).

Oh, and I guess the section of trapeze hoop you connect the cleat to needs to be able to take a lot of shock loading...