Some more panel work this evening. Drilled and deburred all the small holes (1/8 & 3/16) around the panel.
I'm mounting the bus bars to the back of the panel. The other way I can think of now is to use countersunk screws - and countersink the holes in the panel. This will leave the front of the panel flush. Current plan is to laminate a feature "plastic"panel to the face of the alloy main panel sheet - so any mountings must be flush.