The rudder mount suggested by the kit looks like:

This design would certainly work, but I didn't see a good way to assemble and paint it so there was no exposed wood and I wanted to be able to remove and replace the rudders. I bought some little brass hinges at the hardware store and used it for a rudder mount. Doesn't look very salty, but it did what I wanted. Here's the hinge mounted on the hull:

Mounting the hinge was the last thing before glueing the deck and the hull together. The assembly manual recommends placing the hull on the deck and working super glue into the joint with a small artists paint brush (good thing the hatch ring isn't on yet). I followed directions and wasn't very happy with the result. The hull deck joint was not uniform all around. Some places it was tight and hard to get any glue into; others it was loose and didn't make for a good bond. I also managed to drip some glue on my nice paint job, which required some sanding and touch up paint. The resulting joint is strong enough but it leaks a little. If I could do it again, I think I'd just run a nice fat bead of RTV all around the inside corner of the deck and push the hull into it. As you can see in the photo above, the deck is a little longer than the hull, and has to be cut off or it will interfere with the rudder.
Another little problem with the recommended glueing technique is that it's easy to drip glue down the outside of the deck, which results in this:

This only happened on one of the hulls, because on the second one I was more careful and I put a sheet of waxed paper under the deck.
Here is a picture of the completed rudder assembly: