Oh Boy! I've been wanting to do something similar (those brazed on dia-compes are too cool), but haven't been able to find one of these in my size. If you're wary of using a board to do this, Park does make a tool that makes the process seem somewhat more sanctioned, although it's the same action. IF there's a bike co-op in your area, I imagine that they have the tool and a volunteer who has used it in tandem with the other requisite alignment gauges before. Building wheels is fun, and a worthwhile thing to try out. I would also advocate measuring bb dropand comparing with your current 650b before sinking a lot of time/or\money into the 650b party. A bike shop should have a sizing pillar to tell you the size. My guess is that it's a funky size.