I've never been satisfied with the rear cargo area tie downs.. The front ones are okay, they are screwed into metal support underneath, but the rears just into plastic.
So here is my 10-minutes and 10 $ solution for some sturdier mounts!
First, loosen the left and rear 7mm screw and pop out the whole piece
On the next picture, you see upper left the original mounts! Just a bit reinforced plastic! So I used the bolt in the middle of the pic and attached an eyelet / d-ring there
Third step is cutting out a small piece of the rear plastic cover
Then loop a tie down strap trough the d-ring:
And you're done! Here how it looks when in use:
Open the cargo floor, and let the tie down strap hang into the storage boxes underneath when you don't need them, you'll only see a small opening where you've cut the plastic piece:
Hope that helps one or another..