I came back from golf, did a couple hours of chores and then was able to get back to the plane.
I mounted the side supports, making two large bays: the Garmin Stack and the GRT area.
The bay has a shelf (not yet installed, blue in the photos below) to hold the AHRS. This will put it almost on centerline. The shelf will also support the Approach Fast Stack and an avionics fan. The ADS-B and the GRT GPS will sit under the shelf.
Today was a very productive day.
Next: mount the shelf, add lightening holes, then countersink, match drill, debur and rivet. I will rivet the front angles to the front panel, then send it out for powder-coating.