Fuel overflow problem

Fill header tank last so you can over fill wing tanks with the return line... just being a butt-head... Do let the hearer tank drain before filling wing tanks. the return line will drain/ flow back to to the mains if the header is to full...

I have a possible cause of my fuel overflow problem and fuel leaks:   I may have filled the left tank too fast under estimating the amount of fuel in the tank.  Filling too fast may have created an air bubble which caused the fuel to "bubble" out of the tank and because of the wing's dihedral the fuel migrated toward the wing fairing and down to the fuselage ending up as a leak down the lower left panel below the fuel primer.  When I taxied back to my hangar and again opened the fuel cap more fuel "bubbled" out.  I opened the sump drain for several minutes until the fuel level went below the top of the tank and the dripping stopped.  

I flew the plane the next day for about 45 minutes burning about 3.25 gallons.  No leaks, drips anywhere.  Comments/suggestions ??