I've been looking at how the space saver wheel fits in the wheel well. Even though it's a tight fit it can still rock or wobble up and done fore and aft. There needs to be a support for the rim in front of the crossmember. I did some playing around and figured I needed a support about 16 mm thick so I tried a piece of particle board. See photo below. You will also notice the piece of 3mm thick rubber I used as a cushion between the rim and the crossmember.
This made the wheel rock steady. The exact thickness may change by a mm or so depending on whether or not it sits on the black tape you can see. From TeePee53's post above the factory set up has two support pads which do the same thing. My final version will be made of rubber or similar and probably like in TeePee53's picture. I'll post photos once I have it all done. This lockdown is slowing up my progress.
While doing all this I took out the plastic trim that runs across the rear lip of the hatch opening. This gave a good view of the spring loaded buttons that pop the hatch up when the release button is pressed. I noticed a detent on the buttons which when depressed fully and rotated anti clockwise about 20° would lock the buttons in the depressed position. I thought, why would they make it like that? Then I remembered how fiddly it was to remove the plastic trim past those buttons. With the buttons locked down the trim was so easy to remove/install.
If you look at the left hand button in the left hand photo you can see the detent at the right on the bottom of the vertical slot in the lower casing of the button.