To get to the rear deck, you have to remove the bottom and back of the back seat, and the side panels.. The seat bottom is easy, push the bottom section back about 1' from the door on each side, and it pops up and out. The seat back has 5 screws, 2 8mm at the top and 3 13mm on the bottom. Then you have to pull the bottom part forward to get the leather unstuck from the panels and then lift the whole frame up about 1". Careful removing it as the bottom brackets have sharp exposed edges.
The side panels are a pain because after you take all the screws out, there is a sticky hard rubber sealant around the top edge that has to be cut free. You also have to completely loosen the top door trim panel. It has 3 screws and 2 push clips. Also you have to remove the rear speakers which means the rear speaker covers.. pry the bottom edge out first.
Be careful around the seat belt rail, the side panel is only 1 piece of plastic in the shallow cutout, even though it looks like 2 pieces. The whole panel has 4 screws including the clothes hanger, and 3 or 4 push clips. All of the screws are visible, so there shouldn't be any surprises.
When you get all this stuff off, you lift the rear deck up and and take a couple of bolts out, and the tray can then be removed. Seems like it would be easier, but like all things on the SC, nothing ever is.
Let me know if you need a pic; I currently have the rear panel out on mine.