Well, I don’t think I’ll need to throw this junk frame out just yet…
This Trek 820, if I can graft a new rear triangle onto it, is convertible to 650b (with Confreriés, of course) and I probably won’t need to do anything fancy to it except for repositioning the canti studs I brazed onto the fork.
It’s too small for me, but it’s probably a good size for someone 5-5½ feet tall, if I can find someone willing to be a test subject. I could graft an xtracycle rear triangle onto it and build it up as an mtb 650b xtracycleb! (or a bobtail triangle and use it for cyclocrossbing)