[Chris Fultz]

There are benefits to square tube and to 8020.
Weight wise, 8020 and 1/8" al are about the same.
8020 is about 2x 1/16" wall, which can be used in many places.

I really like your attachment approach, which provides a big weight savings and space improvement without the corners and extra bolts and t-nuts commonly used.

Very nice, and way to take advantage of capabilities you have and materials you have and come up with a great finished product.