What a fascinating thread! I had no idea that Doug Fattic had flirted with the idea of titanium brazing!
I've got a pretty detailed writeup about Pino and Cecil's wacky bikes on my (very much unfinished) website, in the 1970s section. One of the things that Cecil worked on was a chemical agent for preventing the uncontrolled flow of the filler slurry used when oven brazing a ti frame, which makes it seem like braze diffusion is a real problem. They baked their frames in industrial quartz-argon ovens... But I've always wondered if a similar process could be done by hand with today's shielding equipment.
https://early-titanium-archive.neocities.org/70s.html
I also interviewed Mike Augspurger about his "lugged" (more like sleeved) welded ti frames. The lugged/welded option is another route you could check out, if you're dead set against adhesive bonding a frame.
Last edited by 3dvvitch; 11-24-21 at 05:18 PM.