Has anyone found a 1/2" aluminum slab for pizza, or priced one from a metal yard? Seems like a good idea. You'd need the slab to be at least thick as your steel (ideally thicker, if you're trying to match the heat capacity) but it would still be lighter.
You'd want to season the thing like cast iron, to blacken it and increase its emissivity. Kenji's test of of copper vs. steel showed the copper to be inferior despite much higher conductivity. Uncharacteristically, Kenji made a dubious analysis of what was going on, but if you dig into the comments thread, you'll find some physics-minded people who correctly posit that the difference is in emissivity, and that a pizza steel / stone / oven deck heats primarily by radiation and not by conduction.
