Adding dimensions to a square or rectangle with rounded corners is easy. In addition, a Quality Inspector can measure fabricated parts with vernier calipers and a radius gauge.

A six sided polygon is more of a challenge. The overall X and Y dimensions are easy to document and measure as shown below. The lower two corners can have their radius documented and produced parts can be QC checked in a similar manner as shown above. The remaining straight sides (black) and corners (red) are more of a challenge. The intersection of sides has been cut away by the rounded corners and the obtuse angles prevent easy assumptions of "horizontal" and "vertical".
Documenting this for fabrication in a manner that is supportive of Quality Control Acceptance Tests (measurements) at production time makes this even more of a problem. How would you do it?

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