[MrForbes]

Nice paper, thanks!

I like the mention that 7/8" round tube will fit into 1" x 1/16" square tube....and also remember that 3/4" round tube will fit into 1" x 1/8" square tube, so you could cut the center out of a long, heavy square tube, put some smaller thin light round tube in, and rivet it together at the ends, should be plenty strong if there are no parts attached in the middle.

Black ABS sewer pipe is considerably lighter than PVC, and it won't shatter either.

Using sheet aluminum brackets, riveted to the ends of thinwall aluminum tubing, seems to work pretty well, and could save some weight compared to other construction methods, and doesn't require welding or milling.

Look at using plywood, it's surprisingly light and stiff, and it's also easy to cut with a jigsaw and a hole saw.