This model is heavily inspired by GeoDave's work on Thingiverse although I designed it from scratch on Fusion360 to match the specific metal bracket I bought (8x10 inch).
.
It uses ½" EMT (electrical metallic tubing), at first, I also considered using ¾ (double the cost), but given I was going to secure at every wall stud (16" apart) ½" proved more than enough with zero flex.
.
I aimed to tie everything (EMT to adapter and adapter to bracket) with zip ties which also proved to be enough and secure, but you can use screws and nuts if you feel like it.
.
The cover picture is the finished project, 8 ft 8" in length (I still bought 2x 10 ft EMTs and cut to length with a pipe cutter)