I cannot stress this enough

Support the steel you're using for your ways!

I realised this afternoon that I had made the same mistake again. Frustrating! This time it was on the narrower piece of steel that will become the ways on my cross slide and topslide. I had stored it unsupported, and it developed a 0.8mm bow. This would be acceptable in the slideways, as it would be a much smaller deviation across their length, but I want to use it as a scraping reference for the front bedways. A 0.8mm bow is certainly not acceptable in the front ways. I've clamped it to my workbench under the bedways to straighten out, but still, bloody annoying.