When I carpeted my car I actually purchased extra carpet and carpeted the floor of the foot boxes. I also have floor mats and did use the lift a dots on all 4 corners and they work very well at keeping the floor mats in place. I would do as JAMO suggested and have a carpet/apholstery shop sew in a rubber heal piece where your heels will be moving from shifting, braking, and applying the go pedal. I was seeing some wear there and just had a piece sewn in. I also carpeted the rear wall and the curve in the corners. Makes for a very nice finished look.
I never carpeted my trunk, because when I built my car I took all the aluminum panels out of the car and had them clear anodized, some for appearance, but mostly because it protects them and makes them easier to clean up.
Here is a picture of how the clear anodizing looks slightly different.
Here is a picture showing how it will look if you don't carpet the piece in question above.
Here is a picture of my heat shielding in the 2 foot boxes:
