Hey folks,
I've received a couple PM inquiries about the convertible rear seat/sundeck in our Volanté so thought I would post what I hope is accurate description of how the sundeck is attached to the boat and how it converts. I will post some more detailed pics when I get her unwrapped for spring commissioning. I will of course defer to Ron and Dan Tanis as the absolute authority in case I've missed or misrepresented anything.
With the seat in the down (sitting) position, the seat back is only attached at the upper corners at the aftmost top side gunwhales. Imagine a small diameter metal rod that spans inside the top of the bench seat (I'm speculating that there is a full length rod - it could be just a connection at each seat back top - it's all under the upholstery so I'm not able to see it fully).
This "rod" is attached to the gunwhales in a small metal bracket on either side of the boat - think of a simple closet bar with 2 U shaped cups on either side attached to the wall - that's essentially the design. There is a small diameter clevis pin through the top of the U cup to secure the bar in the cup. The ends of that rod have a counter-sunk screw head so it allows a small adjustment to the overall length of the rod. It's that screw head that sits in the U cup.
The seat base does not sit fully on the floor in the down position, it actually rests on 2 wedge shaped pieces that are up against the gunwhales on the floor of the boat - it leaves 3-4 inches of vertical space under the seat where I can put a fully deflated skitube or two.
Notice in the Flickr pics mentioned earlier in this thread that the hand-hold bars on either gunwhale (near the speakers) have a unique shape to them - this is by design as the horizontal portion of that bar becomes the support for the seat base bottom when it is hinged into the up (sundeck) position.

When in the Up position, you rest the seat base on the top of those brackets and then there is a single hinged pole that manually comes down from the back of the seat-back and drops into a small recessed cup in the aft floor panel that is the rudder access panel. Since that pole is attached to the seat back (not the seat base) it prevents the seat base from hinging downward and maintains the rigid sundeck.
Here is a pic I found online that is somewhat similar to the type of hinge that connects the seat base to the seat back - this isn't exactly the right one as the AmSki one allows the two surfaces to flatten back completely for sundeck mode.

Hope that helps but drop me a line in this thread so everyone benefits from Q&A's.
-Don