I wouldn't bother with aluminum atall tbh. not really suited to ants, not strong enough at the small thicknesses.
you can probably get away with 1mm polycarb/hdpe (so your 0.8mm might be of some use) just think about angles and atachment. a one piece shell made out of a single piece of folded polycarbonate can be quite strong, spinners may punch a few holes in it, but some of those can also punch through titanium aswell. I'd say look at existing antweights and how they are built, and also joining the antweight forum for more help.