No disrespect Dave, but I don't entirely agree with your philosophy. Some people don't know jack about bikes or bike fit but many of us do. If you don't know anything and have a trustworthy builder, like yourself I'm sure, go ahead and let the builder make the decisions. If on the other hand you have experience in what works for you in terms of fit and have a strong preference in terms of what kind of ride quality you want, and have ridden enough frames to discern differences between different frames/tubesets, then go ahead and enter into a collaborative effort and don't be afraid to ask questions and expect justification from the builder as to their decisions.

Not all framebuilders are created equal; some may be good craftsman but not the best in terms of fitting people. Other builders use the same tubeset for almost all their frames regardless of rider weight and intended usage. In either case, knowledge is your best route toward getting a frame that truly suits your needs, and you need not be a sheep during the process.