I took the plunge and drilled the holes in the chassis rail extensions that Humber so generously put there for me. The controller tray is the stainless steel tray above the red circles.
This is a view in through the front of the car where the radiator block-out panel normally lives.
Close up. We just use a stainless steel 'L' bracket. I have yet to drill the holes in the the controller tray.