Sharpest aperture on the HC 50-110mm f/3.5-4.5 Lens?

[Geruvah]

I found that f/11 seemed to be the sweet spot for my XCD lenses. I'd likely be shooting about the same, unless it's the good ol' Sunny 16. But what would be the sweet spot for the HC 50-110mm f/3.5-4.5 Lens?

[JCM-Photos]

You cannot speak just about a lenses sweetspot, what's important is the sweet spot for each individual image that is a combination of lens performance and depth of field.

For some images depth of field benefit is of greater impact than lens performance loss by diffraction and f:22 can be the best choice.

Or some images with only details in the center and no edge details f:4 can be a sweet spot, using the same lens with a  subject that has many details in the corners f:22 could be the best choice, because this lens has a lot of field curvature.

And when you change focusing distance the performance of a lens can change or not dramatically. Some lenses that have stellar test results (at short distance) are much less performant at infinity, and others that are not winners at a short test distance are stellar at infinity...