|   Is that better for a singlehanded boat in deeper water?

I would ask you. et. al.

|   I don't mind drawing 5 feet, which should be a lot of foil for a lighter 12m proa, in which case I'd rather have taller rudders and skip the leeboard.  I'd want to be able to raise them for shallow draft areas, but not in an easy-up-easy-down sense -- more like every now and then, in which case a beefy cassette that locks with bolts or highfield levers would be sufficient.

Interesting, I was thinking the depth would want to be managed regularly. Tweaked and played with. So lines or electronics or whatever.

|   Plus I know that if I wait long enough, Rob and Steinar will have enough revelations to obviate whatever I was scheming on previously.

IKR

|   As for rudders that flip through 180 degrees, I think you'd be challenged in finding enough clearance for the part that's out of the water to safely rotate if the rudder grounds out and kicks up. You'd have to remove any decking or trampoline between them so they could go through a full 360 degrees. Plus there's also the issue of windage on the section that's out of the water.

I was thinking the part out of the water would be less as the rudder went deep. See pic below. Can not the length be shared? So a fully down rudder should have nothing up?

|   Unless I'm imagining something different than what you intended.

It was not my imagine. I stole it.
http://harryproa.com/wp-content/uploads/2018/06/HarryProaCustom65_005.jpg

As I see it, that rudder can be unidirectional, cambered, and fully optimised, and shared its full length in either direction (carried no extra length of board)

And, apparently, rob has a docking solution for it too, per last message.