I actually could use 650B on this frame. I have a very nice 650B set with Chris King hubs and GrandBois tires on another bike. The brakes (and clearances) have more than enough upward adjustment room to mount 650B on the frame as-is. And I might try it, but that squeezes out a little more of the room to insure no toe overlap with fenders. And I just happened to find a nice used XTR/Mavic wheelset for cheap on ebay. Lightweight and very true. A good find.

That saddle is my adopted favorite model. It no longer is made so I have a standing search on ebay and buy more when they come up.