But ....
From my point of view, and I'm frequently wrong, when you're going upwind the mainsheet wants to sheet in the centre, or pretty close to it. It's when you're going straight downwind or broad reaching that you'd like to keep the clew of the sail down and not have it ride up and turn the sail into a funnel shape. So in those conditions you'd like the sail to sheet from the the hull about a foot or so in front of the crossmember. Take a look at an A Class cat and see where the semicircular traveller ends up. There.
So what you could do is attach some sort of pad to the hull on each side and rig an alternate mainsheet with the hook on the end. Then when you're on that tack you could hook that into the sail and let the real mainsheet off and use the alternate one which sheets down and minimizes twist.
Lots of thrash and sounds like an invitation to capsize to me. But as I said, I'm frequently incorrect.
