you can build a proa - that will steer itself in most any conditions -
but it's going to be really hard to do
that - surfing into a beach with breaking waves -
especially when there is not much wind to use it to steer for you !
or coasting into your slip .......
so you need ruders - but you do not need
anything below the hull -
to keep you from beaching the boat - to run over some tree floating around .......
so you put them on the side - you have
an asymetrical boat anyway -
and supprise - it is at least as effective as on the bottom - because of the endplate you surely have there all the way over -
you want to put them on the windward side - because there you are closer to the center of the boat -
and you will not have the drag of the ruders acting against you .....
also - there they are safe if you are drifting on to a beach sideways -
because they will turn upward out of the way automatically ....
also - on changing directions - you can
use every hand you have - so why not use your feet to steer ?
to begin with ? loops for your feet or legs on control lines is all you need .......
one more thing to remember is - if you
want a safe boat - you will have some way of keeping every thing
from getting wet -
and this will most likely be a vector fin - unless somebody thinks of anything better -
and this fin depends on the free movement of the boat sideways for it to work -
so the ruders should not be to large for it - and freely moveable - the mainhull should not be to deep for it .....