I like Luiz's design, very much outside the box. The rudder would be very much vulnerable while halfway down. The delicate (thin) trailing edge would not have much support. I would think it easy to damage while inserting/removing it, or if you hit something with it halfway.

How would the blade stay in the half up/down positon?

My only other thoughts would be sand jamming the blade into place. Could you trust it in a Worrell style situation to "kick" up as you hit the beach?

Nobody else has addressed the thing I said earlier about the rudder getting jammed into the sand backwards, but if the blade was only half down, the likelyhood would be reduced.

I also wouldn't want to have to be in the back of the boat for a rough lemans style launch....gotta keep the weight forward.

sorry....rambling....

p.s. the mod Hobie thing...it tough to explain, you would have to see it.