The knees are definitely the most complex shapes on the boat. None of the angles are square and almost none of the sides are straight.
It looks like you are pretty close already. The only way to continue from here is to put it in place and mark areas to shave off. Shave and test again. And again. And again. Until the gaps are small enough to fill with thickened epoxy.
The top will stand a little above the sheer, just as it does in your photo. You'll have to sand or plane it down to match. Final shape of the top surface is a matter of esthetics. I rounded mine a bit to match the curve of the transom. My pics aren't very good. I'm sorry.
I've seen otherways to do it. Lots of pics on flickr show different ways of finishing it off. Check there for ideas.
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