I think I've found my problem. The "bolt" has a reduced diameter (waisted) in the position of the contact with the tank. This allows the upper washer to move around as one tightens it up. My solution was to create a land for the washer with solder. I think the pictures explain it better.
The first picture shows the reduced diameter. The second shows what that allows the washer to do. The remaining two show what I did and how it seems to help.
It's not pretty and certainly not concours, about which I don't give a ... er .... hoot.
I did put some Loctite 567 on each side of both washers and re-assembled. Both washers are nicely centered. I'll be filling the tank with oil tomorrow and report in a week or so as to the results. If it's like before, it will show signs of leaking without running the bike.
Gary