Bill's maths concludes 0.057mm, and I can't argue with it. But I would add a note of caution: it depends what you mean by 'super sharp prints'. I have done experiments, and found that people can easily rank the sharpness in 10x8 prints made from negatives that were slightly out of focus, but stll well within the standard CofC limits. Not with loupes, but looking at 10x8 prints from a distance of a couple of metres.
One conclusion that I have come to is that 'acceptable CofC' depends on the quality of the lens (and other components in the chain). If you have a very good lens (film, etc), you will only tolerate a very small CofC, possibly one-tenth the size of the accepted numbers. With a lower-quality lens etc, you can can accept a relaxed CofC, essentially because the sharpest point on the print isn't really very sharp.
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