I wish I had a picture to share. Been right there a few times over the years but never snapped a pic. I never found anything holding this odd diamond shaped board in place to the car. Only a scribble of glue holding it to the headliner fabric. They came right out with the headliner.
There was a piece of black paper material beneath the hardboard package shelf, and I'll assume the bottom of the C-pillar board didn't interfere with any of that on the assembly line.
A lot of owners are using a thicker material today, like dynomat or other, for better package shelf insulation and/or noise reduction. If you plan to use something thicker than OEM you might try to raise the C-pillar boards a 1/4" and affix them to the car with something.
