That’s very helpful. Thanks.
I certainly want to keep drilling through fibreglass to a minimum (preferably zero) so the idea of attaching to the toerail is interesting. My only concern is whether the strength would be adequate. With a shock load, I would think anything would have to be able to support 3x a persons weight. That’s, say, 225 kg: not a lot, I suppose.
My other thought was to attach jackstays to the mooring cleats, but they would have to be very quick to fit and remove. Perhaps a large loop at both ends, then poke through the middle of the cleat and pull the loop over the two ears (I’m sure there’s a technical term for it). Length would be fairly critical so it would probably be best to get a rigger or sailmaker to sew up one end, then fit them to the boat, mock up the second end and take them back to be sewn properly.