Updated to say that I paddled and sailed the original for several months - and I love this little boat! The thwart gives one a very comfortable position, and sailing is done facing forward, with no need to move around. She is fast, flat and stable to sail, and the simple outrigger system works amazingly well . . . hiking consists of merely scooching over, or casually leaning, to one side or the other.
As for paddling, she moves along quite easily, and is - really - the most stable human powered boat I have ever been on. She feels like a dead solid platform on the water - but paddles effortlessly. She'd make the best kayak fishing platform I can think of.
** Also, Splinter can be built as a 15' / 4.57m long boat, givng a little more room and capacity. **
Yes, the ama in this case is merely a "2x4" - the modern version of the sticks or bamboo poles that have been used on outrigger canoes for thousands of years. This is a "tacking" outrigger: One sails her just like any other boat, with the ama alternating from windward to leeward depending on what tack you are on. It works as a counterweight when upwind, and a float when to leeward.
Plans are in both English and Metric units, and - as always - the well illustrated building guide covers everything you need to know to construct the boat, including sources for fabric, sails and hardware, as well as detailed skinning instructions and sail and outrigger options.