I worked for a large union sheetmetal shop. You wouldn't Believe the scrap they throw out. They had a large roll off bin out behind the building, the kind that gets pulled up on a 10 wheel truck. I still go over there on weekends and grab some metal to have on hand when an idea hits. A nice smooth piece 3x4 might take some time to get ahold of, but I found 3 lengths of 10'x 9" that was broken into a "U" shape that made PerFect Raingutter when I fastened it together, then put some home made end caps on. It's been on my workshop for Years. It is so cool to get stuff for Free! If you are in the city, the larger the better, get in the phonebook and look for sheetmetal shops, 'drive by early saturday morning with a cup of coffee and see if these places don't have one of these scrap bins. My shop didn't get paid for the scrap, they got it hauled away for free. 'Might be worth a shot to speak to someone there and lay the 'ol, "the kids are hungry and bills are all due" line on them