I have.. Several times. Just installed a new tank, sending unit and gasket. I thought is was leaking out of the vent. but it just kept getting worse. I was hoping the problem would go away with all the new $#!+ I threw at it...NOT! I could actually wiggle the sending unit as installed.Tank is a Spectra. I think the flange material is thinner , but my old tank is an original and it's all tweeked out too. I ended up taking the gasket I made for my old sending unit and installing it and so far, so good. It's made from sandwiching cork between paper and it's a bit thicker than the rubber pos. Man I hope it doesn't leak again. If it does I'll make a thicker gasket.
Well I went and checked it before posting, I did fill it up and it is dry at the gasket but it leaked out the vent pipe a little. So I cracked the cap and it had a little pressure in it. here we go again??????