[John]

I dont think this steel is going to make for a good sway-bar. The reason is that it may not have the spring qualities that a sway/anti-roll bar needs. It all depends on the grade of steel; though, you don't see many stainless steel springs outside of very specialized applications.
Why stainless anyway? the cost for spring grade stainless is going to be huge, and probably perform less than a non-stainless bar.

bending tube on a pipe bender is going to be a problem as well. I might have this backwards, but pipe is measured on the I.D and tube is measured on the O.D. This means that the dies used for bending copper water pipe are not going to fit tubes.

You also cant go bending spring steel with out heat. This is a problem since when you heat it, the spring is going to lose its temper. Thats why a lot of sway-bars for race cars have splined ends which removable arms attach to.