I went ahead and took the plunge. The jury is still out, I may or may not be happy with how it turns out.
But I bought a $20 barrel and $16 worth of rubber sheet metal edging.
I cut both ends off the barrel using an electric shear. I bought that for $10 at a flea market more than 5 years ago, and this is the second time I've used it. But for this job it was perfect.
Then I sliced the barrel lengthwise and cleaned the inside out.
The barrel contained some kind of water soluble emolient, and its only warning label was "harmful to aquatic life". So I had to be careful not to let any of it wash into the yard or down to the stream. So I had to go through a bunch of paper towels to mop it up and wipe it clean.
Then I uncurled it with my hands and toes. That worked but the ends were curlier than the middle. So I laid it on the floor and put a 2x4 on one curled up end and rested the full weight of my shop press/welding cabinet on the 2x4. Then flattened it downward. That made a huge difference.
After working both ends, I got where I could flex it to the arc I want, but it wouldn't hold there.
So I ran some 1/2" EMT conduit through the pipe roller and gave it the desired arc. And then cut and welded that into a frame.
And then put about 75 lbs weight on the sheet to flatten it downward while I screwed in drill tip screws to attach it to the frame.
I've since painted both sides, and tomorrow after it's dry I'll apply the rubber edging and then decide how to mount it.
I'll post a few final pictures then.
I think it's going to look... only "ok". Not great. But not awful. There are so dents visible from its barrel days, and one large kink where it didn't uncurl cleanly.
I suppose for $40 invested I'll hopefully be happy enough.
Bob
ain't no dummy. I held off on buying the set for 175, based on a request to "think about it overnight". Fair enough.
myself out of a hole!!!
to tell her! 
