Most cars have something like whats pictured in the link. Most vehicle trunks have 2 sets of notches for multiple systems (for different markets) and that looks to be the case for the Focus. I see a second set of notches, but I wonder if its for some type of tray with storage that goes under the hard shelf.
Check out the link and let me know if you've seen anything like it for the Focus. I find the trunk so small that I dont want to limit it's size even more with a hard shelf. I would rather have a soft shelf that you can easily stow when you need the space.
https://www.google.com/search?q=car+ret ... 3IWdXRROoM