I've wondered about how sizing converts as well. Been thinking about building up a townie for my wife so she'll have a bike that's worth riding on her occasional commutes (and maybe if she's got something nicer than her x-mart special that she's had forever and hates, she'll go riding with me occasionally). The question of how reach changes when you're sitting upright with bars that sweep back and are at/above saddle height (and how to achieve that), are things I've been thinking about. The fact that I'm trying to figure out how to do it on a step-through/mixte frame for my 6' tall wife is another complicating issue due to rareness of frames, but, as with you, I'd love to know how fit converts over.