Before I realized Spectra might send me a new tank, my first thought was to use JB Weld or Marine Tex to fix my flange. I don't weld or braze so I'd have to pay a radiator shop or someone to do it for me.
My brother JB Welded the engine cover onto his Honda 750 about 20 years ago and its still on the bike and doesn't leak a drop of oil. He laid the bike down and sheared the cover clean off. I have no problem believingJB Weld would stand up to the task of holding that flange in place.