Well, to maybe close out this thread, I was able to drill out the holes I was concerned about without the right angle drill attachment. I got all 30 rivnuts installed, and yesterday and today, with the help of my 27-year-old son, I got the Safari Gard rocker guards / rock sliders installed. I'm very happy with them. They stand proud of the sills and the doors more than I expected, providing more protection. FWIW, they show no signs of having yet been anywhere near a rock or any other kind of obstacle.

Also, Alex_M stopped by a couple days ago and picked up the wheels and tires, as he described in the "What did you do with your DII today?" thread.