Wow, that's a nice level of craftsmanship. Perfect fitting. Have you ever considered making those tanks in a way that they would not go around the headtube? I was considering buying a very rare Polish-made Universal/Tyler Korlis girls frame, that would be a shame to cover the front badge on the headtube.
Cut a hole in the front of that tank in the shape of the head badge, then fit a magnifying glass into the cutout to bring the head badge forward.