This is an interesting one (maybe even to you, rather than just to me, for once). Why?
-650b wheels. Ok, not that unusual these days.
-Coupled. With a custom Ritchey-style seat lug and S&S on the downtube.
I get a lot of questions about travel bikes and couplings, so here's a quick rundown (you can also read my old FAQ, from, gah, 2007, on S&S here)
-Dual S&S couplers are the most flexible system in terms of tube choices (any diameter, basically) and can allow big, big bikes to fit in a case, thanks to the fact that they can go pretty much anywhere on the top and downtubes. They are heavy (300+g for a pair) and require a special wrench to keep tight. They're not cheap - $500 for parts and labor to get them on your frame. If they do come loose during a ride you won't destroy your frame - you'll just notice that something is rattling/feels weird and have to stop and tighten them.
-The Ritchey Breakaway system is cheaper ($250) and lighter (only adds maybe 150g). Downsides are tube choice (downtube has to be 32 or 35mm) and the seat lug/coupler placement means that larger mountain bike frames won't fit in the case sometimes. Some people also don't like the look, and if the downtube coupler (a hinge clamp held together by a single M5 bolt) did loosen/release when riding, I think you'd break your frame in half. It also has to be modified for most mountain bikes. The seat lug supplied by Ritchey is also made of petrified whale poop or something and is not a good size for attaching anything but a very small toptube. You're stuck with a 27.2 post, too - though that's usually not a big deal for this kind of bike.
-The system I've decided I like best (assuming you're not just going to get an FS bike and take the rear end off to pack it - that works great!) is to use an S&S coupler on the downtube and a custom-made seat lug (allowing some choice of toptube size and seatpost diameter). It's *mostly* the best of both worlds, though if you're riding a bigger frame it's not always workable if you want to fit your frame in the S&S case. Weight is in the middle (200 extra grams, maybe?) and so is cost ($400).
And that's the system I used here for John's bike. I think it came out pretty nice!
Geometry details tomorrow.