Use a thin composite shell (honeycomb or foam sandwich) plus minimal hardware, and avoid aluminum extrusions except where you need edge strength.

• Panels: Use 6–10 mm PP honeycomb (Polypropylene) or a 3–6 mm foam-core sandwich with thin fiberglass skins; both beat 9–12 mm birch flightcase ply by a large margin for weight.
• Edges: Replace full “double-angle” aluminum extrusions with light U-channel only on vulnerable edges; reinforce corners locally with bonded patches instead of heavy corner blocks.
• Hardware: Use surface-mount butterfly latches, lightweight sprung handles, and plastic corners where acceptable; keep hardware count low and place it only where loads are real.

Alternative: If you need maximum durability for touring abuse, use 6.5–7 mm birch ply with standard extrusions but aggressively reduce hardware (two latches, one handle per side, small ball corners).