As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON REMOVING BOTH WINGS TO INSTALL MONARCH PLASTIC FUEL TANKS, THE REAR SPAR INBOARD ATTACH BLOCKS, LEFT AND RIGHT, WERE FOUND TO HAVE INTERGRANULAR CORROSION IN THE INBOARD SLOT AREA ABOVE THE LARGE BOLT HOLES. CORROSION AREA ABOUT .50 INCH WIDE BY .1250 INCH DEEP FROM TOP OF BLOCK TO BIG BOLT HOLE ON INBOARD FACE OF SLOT. THIS AREA IS IMPOSSIBLE TO INSPECT VISUALLY WITHOUT REMOVING THE WINGS.