Try a different manufacture. All of them build slightly differently and a 51 in one may fit aswell as a 53 in another. Get out and test ride a few bikes.
I "Like" a 51cm with a 53.5cm top tube- but can ride a 49 or a 54 and have all 3 fit me. In fact I do.
The critical bit for me is the top tube length- not the frame size.
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How long was I in the army? Five foot seven.
Spike Milligan