Back when I was still using 100W panels, I actually built solar array frames out of steel sheetrock plaster edging. Yes, the stuff you can tie knots in with your hands.
I started building frames screwed together with 10gauge machine screws, but then I got a welder and found welding was better.
The edging was really flimsy, but by incorporating diagonal supports every 12" or so, was able to make frames that held up for years. Look at the construction of any overhead highway sign, and mimic that. It will work!