Acrylic I used 1/4 inch thick, 2 sheets 18 inches by 48 inches and 2 sheets 18 inches by 36 inches estreetplastics.com
6/32 by 1 inch machine screws
3D printed brackets--design and print files here:
Building this in a "U" shape is critical for strength. The brackets hold everything together and secure the acrylic to the plywood base.
You can't swing on this like a gorilla or something will probably snap; but this arrangement survived two days at the San Mateo Maker Faire, so it is workable.