Couple of things I would consider - rivnuts are known for coming loose. I used some in various places and wish I had not.
You probably want to keep the wiring runs as short as possible, to avoid having to put a fuse in there.
I mounted my IBBS on the rear bulkhead of the front baggage area, and it's very close to the things I plug into it - my GRT EFIS, GRT EIS 4000, and my GRT Safefly 2020 GPS.
If you want to mount it there, I'd mount it on the under side of the plate that will cover that area, with a service loop to make easy to remove, avoiding the rivnuts.