I have a question - How much of the PBP today is still ridden on cobblestones? Is it really necessary to pursue converting to 650B with the extra time that would entail vs. riding it on, say, 32 or 38 mm wide tires?
If the answer is that 650B is a must-have, do the maitres-de-randonneur like @
gugie and Peter Weigle ever build ahead so that a properly converted frame could be sourced more quickly than waiting for the right donor bike to come up for sale and then go through the modification, paint & build process?