Building up a bike for my sister in-law. She's 5'5" or 5'6" and average proportions. Would like to go with the Zion 737 with gears. Looks like a size small would work for her but how about some real world help with fitting the Zion to a smaller rider? The $249 deal for frame/fork just looks too good to pass up.. Had her on my 16" Mary SS this past weekend on some rail trail and she did fine although a shorter stem would have certainly helped. Afraid if the 737 doesn't work out I'll be going with the 26" Zion.