With the avionics positions determined, I finalized their mounting attachments by updrilling all the pilot holes to accommodate #8-32 machine screws, installed matching nut plates on each mounting hole, labled the avionics positions on the shelf, then mounted the avionics into place with screws.
From the top: Mounting holes drilled, nut plates installed, avionics positions labeled.
From the bottom: The nut plates after mounting.
The avionics mounted to the avionics shelf with screws.