I've sailed a few boats out there and I really like my Nacra system. I've never had the 'creeping' problem that a lot of folks complain of on either of the two Nacras I've owned (both have sailed for 20+ hours straight with the rudders down). I can put the rudders anywhere between fully up and partially down and cleat them. What I also like is that if the Nacra system fails, it fails in a full up (cam cleat failure), or a limp and floating position (bunji breaks). My Hobie 18 with the old style aluminum cams would fail to release from the locked downward position. It is quite a revelation when you come back from a day sailing blazing through the surf only to realize you can't release your rudders.

I really like the idea of the rudder that sits in a box and can be raised vertically up and down. You could make the box pintle points so they would break free in the event of an impact. I suppose the bottom of the rudder could be shaped in a sloping fashion so that when you are beaching you could release the hold down mechanism and let them raise in their trunks as they start sliding on the bottom.