Fabricated the rear cockpit instrument panel from .063 Aluminum. I first made a plywood template that was just short of the fuselage skin. Try to keep this to less than 1/4. I clamped this template in position, and noted the area where the panel will eventually make contact with the fuselage skin. I removed the skin and applied clear packaging tape in this area to act as a releasing agent.
The skin was replaced and automotive body filler, AKA Bondo was mixed up and then squeegeed into the space between the template and the skin. If the gap is too big, the Bondo will slump too much. It this is the case, pieces of pasteboard can be taped to the back side of the template the give the Bondo some support.
After the Bondo sets, the skin is removed as well as the template. I sanded down the Bondo to be flush with the surface of the plywood template, and then used the Bondo-modified template the trace out the shape of the instrument panel on a sheet of .063 aluminum, in this case 2024 T3.
This method makes the panel fit like a glove in relation to the fuselage skin. Repeat for the front cockpit