In the end, I cheated. I ordered a set of rivets from Joe Krybus. Joe supplies these cut to approximate length and with the difficult (angled) end already formed. It only remains to push the rivets into place, trim them to the exact length with a Dremel tool (Joe also supplies a diagram with the final dimensions) and hammer over the "easy" end. - I was able to do this quite neatly with a very small ball-peen hammer.
Here is the first one installed on the top right wing.

and the other three awiting their turn:

Steve