Howdy, neighbour. We had a 1981 #10496. IIRC, the port locker was huge, with a shelf on the aft end for the fuel tank. From my readings in Main Brace and Mainsheet magazines, the advice was to always make sure the tank was well secured. I don't recall anyone posting or writing about separating the fuel tank shelf from the rest of the boat. What that area really needed was ventilation. You might ask around on the other (multiple) C22 websites and blogs. Good luck.