the access is located behind the built-in trash door on the wet bar. You have to remove the door hatch and pull the circular disk that is silicone to the deck to get access to the fuel sending unit. that access is pretty much limited to the fuel sending. to access more of the tank you can remove the built-in storage compartment that is located just aft of the wet bar I believe there's 4 screws. using that access and the engine compartment access you should be able to work on the anti siphon valve.
