With reference to angles of attack:-

On the Stealth, the rudders are held down by a pin through the top of the stock. Without the pin in the rudder moves up and down with changes in speed. As you sail gently in to/out from a beach you can watch the rudders rise and fall slowly. At quite fast speeds (IMO around 10 knots) the rudders are around threequarters down on my boat. So the loadings can not be particularly high. If you sit forward in this situation, as you'd expect, the rudders sink. When you move aft to put the pins in the rudders rise.

This is a useful trait when landing at a beach because all you need to do is unpin the rudders and then as you are about to land, move right aft and luff at the last moment. With these vertical stocks you retain steerage with even a small amount of rudder in the water at these lower speeds.

Interestingly, at Eastbourne a while back, the locking pin came out of one of my rudders on the downwind blast. This provided huge entertainment for Paul Warren right behind me as my port rudder launched itself out through the bottom of the stock! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
I, though, was not amused! <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />