Here's the cheap and reversible cargo net option. The advantage is no cutting on the car, and easily removable.
I made up a pair of flat hooks from 1/2" wide 1/16" aluminum strap, which hook under the front edge of the trunk floor. It took about a half-hour to bend them around a 1/4" drill-bit, drill the holes, and install.
Installed. The carpet is Lloyd's Mats Luxe in Ebony - a near-perfect match.
The cargo net is a 15"x30" from Amazon.
http://www.amazon.com/gp/product/B00...ilpage_o00_s00
It rides a couple of inches above the trunk floor, because the aft loops are above the floor. I like this, because even if you just set something on the mesh instead of under it, the net usually keeps the item from sliding around.