Before riveting all the aluminium angles to the back of the panel, I spray a light coat of primer where the parts will mate.
I then rivet all the angles and the nutplates.



I then make a trial installation of the switches. I will have to buy a feaw more as they are not all the same.



The switches get installed with some wahers. One of the washer has a little tab. So I drill the back of the panel being careful not to drilled through to avoid having a hole below the switch.
The (bad) picture shows the result.