pure drive grommet in an aeropro drive cortex
Since I didn't have the right one on hand, I tried putting in an older pure drive grommet (the one before the cortex) into an aeropro drive cortex, and the bumperguard was too short. I was committed at the point where I knew for sure. At least the last 3 holes on each side needed to be elongated a tiny bit (1/2 a hole width?), so that's what I did with the side of a drill bit. The grommet strip at the top stretched ok with some coaxing.
Bah, never again... Oh well. It worked.