Hi, Bob.
The channels were originally supposed to have a 1" rounded edge on the length as in some of the photos I had, but the sheet metal bender couldn't do it for some reason.
I told them to just leave the edges flat, bent 90 degrees down from the 35 degree bend, and I would do the finishing work. That extra sheet metal was 2" wide on each side. Not wanting to impose on my friend who had done me a big favor already, I took the pieces to a local bender. They took the 2" edge, and folded it back onto itself to make a 1" double-thickness edge along the channel's length. This made them way more rigid. I didn't have to weld anything on.
I keep looking at these drawings, and can't see how someone could reproduce these from what I have presented, so I am going to measure what I have here, and add to it..
The added 3/4 x 3/16" strap used were drilled, tapped and installed using 1/4-20 button-head allen screws, with the heads filled to look like rivets, (34 of them per channel)....my forearms looked like Popeye's after drilling and tapping 68 holes that day!
Thanks, David