I temporarilly installed the avionics trays to find a support point for the GNS430 and the Audio Panel.
I also marked the ventillation holes in the 430 tray to add ventillation holes.
I tried using a fly cutter to cut larger holes. This really didn't work all that well. It loaded down the drill press pretty badly. The cuts were round, but had a lot of junk on the back side of the cut that took a while to debur. I decided that I would use the step drill and drill more smaller holes. This worked pretty well.
Image 2 showes the upper tray all riveted in place.
