I'm happy to report that no drilling is required! Behind the panel fasteners, is a hole that the T-Anchors can self tap into. The top holes on both sides were very tight, and I had to use a pair of pliers at one point on each side to get enough leverage to get the anchors in all the way. (I covered the plastic T-Anchor with a towel to avoid marring the finish.)
Briefly, here's the process.
Assemble the T-Anchors
Locate the panel fasteners on the top and bottom on each side, and remove. I ended up going to Harbor Freight and buying a cheap removal tool. The top ones were a bit of a bitch. The bottom ones the plastic sill were much easier to remove. Screw the T-Anchors in nice and tight. As I said, I had to use a pair of pliers on the tops ones.
Attach the cargo net and you're done