Sounds like your shop is taking care of you. But for the record, I actually went up a size from the 48 cm Ruby I demo'ed for three days, to the 50 cm Synapse Feminin I wound up buying. Specialized and Cannondale seem to size their WSD frames about the same, and it's just that the Ruby felt maybe a weedie bit small on me. For comparison, my old custom steel frame, without a sloping top tube, was a measured 47 cm c-to-c.
Is it the WSD Synapse you're trying, or the "men's" frame?
Speed comes from what you put behind you. - Judi Ketteler