Well, after running out of time and despite some great suggestions, I was not able to find a ready made nut so I broke down and made some. Besides here, I hit up my engineering co-workers and couldn't come up with something. Finally on the last day and the second to last step, a coworker came up and said couldn't I just cut out some aluminium disks like 3/8" to 1/2" thick then tap the center? That would have worked perfectly but I wouldn't had the excuse of buy a gas welder...
link to pics I brazed 1/2" flange nuts onto 1/2" x 2" fender washers. It was very hard getting even heat as you can see on the unpainted fender washers but I did get some good pentetration. 20 plus years of no brazing didn't help either. I then cut the knotches with a bandsaw then spray painted with cold Galvanize paint.
With the panel installed, you can see how the nuts can be adjusted after installation. I have about a +- 1/4" of play for the panel.
Thanx again for everyones input
