I would love to try this, seems like the best way to get lots of nice looking contours.
As far as jigs go, I do believe that, if you put enough heat into something to severely warp it, it would show up as soon as your removed the jig. Granted, that would probably take welding a huge length without ever stopping, but I just wouldn't want a jig to give me false confidence. Obviously a jig is necessary for repeatable results, but I don't think it would stop warping entirely.
I've been wanting to build a go-car from an old 3-wheeler engine I have... could be some good practice on a smaller scale. Cheaper to learn the hard way
