I've seen a lot of posts lately about people wanting to try out a 650b test fit, and realize that really the best way to do this is to put a set of 650b wheels and see how it fits. Room for 42mm Hetres? Fenders and clearance? How about brakes?
I have a set of 650b wheels with 42mm wide tires, also a set with 33's. If someone in the area wants to check out the fit, let me know. I'm in SW Portland, close to Tigard and Beaverton.
A couple of LBS sites that I'm pretty sure would do the same would be Velo Cult (of course), and a dark horse: Kenton Cycles in North Portland (technically the Kenton area).
I've converted a few bikes to 650b, including fork rerake if warranted and cantilever addition. It's much better to test fit a set of wheels rather than just take a bunch of measurements - one test fit is better than a thousand measurements, IMO.