Hi tim_p
The boot liner that I got from my local dealer, is a tough plastic unit, about two & a half - 3" deep. It fits snugly in the boot and it is moulded with the four corners inverted.
You still have access to the little D-rings.
I have found the 'inverted corners' very usefull to place small object to stop them rolling around.
I couldn't get the pictures to show up so I have put in the links to them (in my garage)