McSalish,
My brother in law had this very issue while cruising in the Florida keys a couple years ago. His tank started leaking, so he purchased a 6 gal outboard tank and added a brass barbed fitting to the temp tank for the fuel return. I think he placed it close to the tank opening to be able to attach the backing nut the the barbed fitting. After having the fuel removed from the boat tank which lives in the keel (IP 38), he installed the temp tank to get the boat up the west coast of Florida to the IP factor repair yard. 25k later he had a new fuel and water tank and salon floor. It seams that you have to remove the salon floor to get at the water tank and remove it to be able to remove the fuel tank, which lives under the companion way tucked against the front on the engine. Replaced the water tank because he did not want to tear up the salon floor again when the water tank started to leak. Big job and he wanted the IP repair yard to do the repair so the temporary tank was necessary to get it there. Worked great for the week required to get to the yard. Just had to monitor the one tank and siphon fuel from a 5 gal Gerry can when it got low. Really makes you thank Catalina for making our tanks so accessible!