The leeboards in "The $50 5Hr. canoe sail rig" book, as far as the streamline shape is concerned, looks like it would be easier to make than a balanced foil shape. For those who do not have the book the jist of it is that one side stays flat and you only shape one side. Which sounds reasonable to me since a piper cub wing is flat on the bottom and airfoil shaped on top. To get to my question.... assuming I were able to make a sufficiently efficient asymmetrical foil, would you want the flat side away from the hull, theoretically developing the "lift" to windward or should it be the other way? Also, if both leeboards were down at once would their combined efforts be canceled or would their combined efforts against eachother induce drag, thereby making the case for a symmetrical foil?

Thanks
Red