1/16" Al diamond plate bends more easily than I'd want for an unreinforced keyboard shelf, though it might be acceptable. Pressure on the keyboard will transfer to the plate at the feet under the ends where the plate is better supported by end flanges.
I would first determine the maximum length and gauge that the brake can bend, then see what thickness of aluminum is available in cut pieces at what price. You can adjust the stiffness in the design. The fuselage ribs of a B-17 bomber are only 0.040" thick. jsw