I was quite intrigued by stainless steel, both for the looks and its claimed benefits. But as above, Cy’s discussion of their prototype made it sound like it’s really difficult to work (or work well), and there seem to be very few places that have the necessary skills/ tools/ sub-contractors.
Talbot Frameworks or Rourkes will also build you in Reynolds 931. There’s probably someone in Italy prepared to make you on in Columbus XCR. Because of the harder steel, it takes longer to cut / mitre tubes, wears the tools quicker plus the tubeset costs a lot more than regular steel hence the price hike over normal alloy steels.