I need to build a cabover addition for my M109 and I'd like to make it all out of sheetmetal (steel) with rounded corners and edges. I've got a sheetmetal shop here in town that can roll all of the corners, but I'll need to form the round caps at the top/front corners - unless I can find a source for spun or formed semi-spherical sheetmetal caps. Half-spheres that I could cut to fit would be perfect. Radius isn't critical because I can have the edges bent to match, but the edges of the box are 4" radiuseses. Seeing as these will be at the top/front of an off-road oriented motorhome, I need to make 'em heavier-duty than normal. I'm thinking that anything approaching 1/8" thick would be good enough. Any suggestions? I know I could form them. That's not the question.