Install Removable Bestop Cargo Tray via Nutcert/Rivnut

I am getting ready to design a build for a Bestop cargo tray install into a 14 Dbl Cab Short Bed.

I want to use 8 rivnuts or but certs that are installed into the flat surface of the wheel housing up near the front of the bed that will hold 2 cross braces (aluminum angle) with the cargo tray attached.

What rivnuts? That's the question? Yea I used the search function but not many photos of installed nuts exist? Any cons to drilling into my bed on the flat surface?