Clarification needed: Smallest aperture (highest f/) to use with V1 lenses?

I test any new lens I buy with a chart to be sure all is well before it goes in the bag. The chart is 36x24 inches so the lens is tested at more normal focusing distances. Anyhow, viewing images at full resolution, you are okay at f/8. f/11 is degrading a bit, but very usable. In fact, shooting raw and sharpening can bring the image back to the snap it has at wider apertures because the blur radius is small enough that USM can handle with ease.