Having a try at Billet pistons made from low expansion 4032 alloy (allows sightly tighter installation clearance than 2618 alloy). The advantage of billet is that you are not dependent on an existing forged shape. So you can have them designed anyway you want. The result in this case is the lightest Norton piston so far. The 73.5mm piston in the image below tips the scales at only 177 grams. Note the efficient box shape and the underhead milling keeping the crown thickness uniform around the intake pocket (at bottom). No dead weight left on this shape.