If You use a light core material, the board will be light, stiff and strong. Insulation foam, extruded plloystyrene or pollyurethane will work, but isn't real strong. do not use expanded pollystyrene [white bead board]. The best really light core is plastic honeycomb. Pollyurethane fome [Airex] is strong, and tough, end grain balsa [Baltek] is strongest & toughest.