Originally Posted by jyossarian
Should be fine. But if the frame's too big, you might be too stretched out on it. Also, you'll want some crotch/top tube clearance.
+1
Yeah, 2cm either way is do-able. But, 4cm up is probably too much if you fit a 50cm. It would be heartbreaking for you to spend lots of time and money restoring/converting this bike for yourself and it didn't fit.