I Currently own a Nacra 6.0 and I do not have any problems with the hook and ring system, before the Nacra I owned a dart with the same system.
I do not have problems not on the water or on the land.
The most important is that the cat is facing the wind at all times.
I have seen many sailors who cursed the ring and hook system but I usually got the problem solved for them in one go.
I do not want to brag but I think it is something you must have a feeling fore.