If you are still around, may I ask you a couple questions on the fit? I'm 5'4.5" and am thinking about the 48, don't know if that would be too big for me? What is the stem length on your 48?How did the 48 work out for you? I'm 5'6" and unsure between 48 and 51.
Edit: a few months later and I got the 48. Perfect fit for me.