you may have figured out by now, as i have just recently that the salon deck is just dropped in over the fuel tank. Mine has a ~20 x 20 inch floor inspection panel and eye that you can lift up to reveal the fuel pickup/return and gauge. Extending all around this inspection panel is the fuel tank that has a drop in floor made of 3/4 ply, teak and holly ply and 2x4 stringers about 40 x60 inches. It is held down by gravity and age and dirt in the joints. Lifting it out will reveal the entire fuel tank top, fuel filler and vents, mess of old solid copper fuel lines and other items like bonding wire.
To lift it out I used two pairs of 2x4s on edge blocked up and all thread 1/4 rods to the corners of the inspection panel. A lot of spinning the nuts and the whole floor lifts out uneasily because of the debris in the slot but once out and clean an easier chore. I installed lifting nuts in the corners so no longer require the 2x4s.
You can pear down into the void around the edges of the fuel tank and wish you could use all that lost space. Does this help?
Think we should start a 530 thread for overcoming oddities like these.
does this help