Once moving beyond scraps you might have laying around is on the table and you are looking at new material, I suggest considering PolyMetal or equivalent.
Here is some of the experimentation I did with scraps. It consists of a 3-6mm thermoplastic core with aluminum skin on at least one side (usually both) of .007 or .014" thickness. About the same as an aluminum can, with enamel finish in various colors; available in 4x8, 4x10, 4x12 and 5x10ft sheets. It's used for commercial signage and the big wings on dirt track race cars.
The stiffness of 5/8" plywood at 1/10th the weight. It's more expensive, but the gains in not needing finish work are immense. Rolling and shearing (by hand) worked great but braking failed and dimpling would require a hydraulic press with a bigger throat than what I have.
It falls between hand-formed and planished aluminum and coroplast, in cost and effort.