I know this reply is a little late, but I bought the Small Air 9 frame and it doesn't match their geo chart at all. They list stand over at 28.3 for the small, and after I got the bike all built it was more like 30.5-31 inches. I'm 5'5" and there is negative clearance over the top tube. Niner gave me some song and dance about "the only measurement that matters is the top tube" but this is a myth perpetrated by the cycling industry when sloping top tubes became mainstream. Its not true however, unless you're not worried about whether the top tube is going to clock you (or worse) ever time you have to put your foot down. Its not like we ride bikes and never get off the saddle, from start to finish. Especially mountain bikes.