[artdutra04]

Depending on how well you support it, I've mounted electronics to as thin as 0.060" (1/16") polycarbonate sheet before.

In order to successfully use thin sheet (whether plastic or sheet metal), you have to prevent it from "oil canning", which is where the surface looks really wavy and anything mounted to it flops around.

Riveting a few strips of 1/2" x 1/2" x 1/16" wall aluminum angle to 0.060" polycarbonate can eliminate nearly all of the oil canning without breaking the weight budget.