Like anything in life nothing lasts forever, including impossible to access fuel tanks. This tank was on a CS-36T and ran port to starboard under the cockpit sole behind the engine.
At first I was clearly delusional and thought it may come out through the port lazarette, but I was sorely mistaken.
This photo shows the first step in this project, removing the engine. for removal I enlisted my main sheet, an old boom vang and a 4X4 across the companionway. Once everything was disconnected the engine came out quite easily. I had a buddy there just in case but this can be done solo on this boat.