I had a pair made from 4" PVC, covered in wood veneer.
Inside the PVC pipe was 1/2" threaded steel rod that held tension on the endcaps, which were about 14" square 3/4" plywood, edged in matching veneer. The top of the plywood was black-laquered.
The tubes were sand-filled.
The design was up on the InterWeb, and my luthier buddy put them together for shits and giggles.
I borrowed them for a few weeks.
Here's something close to what they look like:
http://www.ryderstep.com/?p=21