My road bike is about 4cm too short in the frame. (58cm, I "should" ride a 62)
I raised the seat, put a longer stem with adjustable rise, and I'm going to put a wider bar on next. It fits me comfortably enough that I did 35 miles on it last weekend and felt as if I could have done double that.
Frame size is important when considering what components to buy. Do you need a short reach drop stem, or a long reach riser? A short seatpost, or some gigantic Thompson post? I think that within 2-3cm of the "correct" frame size, and you should be OK with just some minor adjustments.
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"I feel like my world was classier before I found cyclocross."
- Mandi M.