As years go by I am leaning more towards Grant Peterson at Rivendelle's theory on sizing. 20 years ago we thought riding a size smaller made for a lighter more agile bike. Actually we just had to go to drastic measures like long setback seatposts and long stems to get comfortable. Now Itend to err on the big side if I am in-between on the manufacturers sizing charts. If I can I just buy according to the cockpit length and stack height (headtube height) I know I need to get the fit right. That keeps setup simple.