Interesting. Pure Ti has a much lower strength. Grade 3 is 450MPa (
https://www.sciencedirect.com/topics...itanium-alloys) compared to 800MPa or so for a quality CrMo or similar tube. But I guess you'll get away with it in 0.9, and people were accepting of more sketchiness in the 70s. They used to use Reynolds 531 (a bit weaker than modern CrMo so long as you don't weld it) down to crazy thin gauges.