I've got a 650b'd Comp GS ('78, I think..), and I don't think I'd want to do loaded touring on it. I like it, and it handles a loaded rando bag fine, but.... bag or not, the steering is just a bit 'lively', to the extent that I can imagine if it were loaded up and I was tired after covering a lot of miles, but still had some to go it might be a bit of a challenge. Though TBH, I have yet to put more than maybe 50m on it in a go. It's a tricky calculus- a bike that feels fun at the start of a long day can be not so fun at the end of the day, as a bike that feels boring at the start can feel stable and secure when the energy and attention starts to diminish. An aside, but my '72 PX-10 650b conversion always seems to feel good at the start of a long ride, in the middle of the ride, and at the end (though I've only ever over-loaded a rando bag on it, never kitted it for fully-loaded touring).