Fred,
My reaction exactly when I took the top nut to the tool shop to buy a socket and realized nothing would fit!
My immediate solution was to curse all frenchmen, a typically british reaction to allmost any problem with anything, french or not!
Then I stumbled across the hole saw and the rest is history.
By the way, the nut is 8 point because that gives a smaller overall diameter. Yes, there is nothing to prevent making the available space larger, but hey, these guys designed the 2CV!
Ron