There's always fudge room in any line. Figure that it's located in a place that covers the worst case scenario of rider weight, fit, clamp design, etc. So if you're not anywhere close to a worst case situation, you're probably OK fudging a bit.
The operative word here is "probably", and that depends on how much Campagnolo erred to the conservative side. Off the cuff, you're probably safe if you still have at least 2" of post in the frame, and the bottom is below the bottom of the top tube, and you're not heavy or ride bad roads.
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