How do you dimension a semi-circular pattern on a print?

I would dimension it very similar than you, just adding the radius for the pattern, the first hole angle and a little different centerline for the holes.

Here is an image. Hope it helps... (Radius is in mm)

I guess this is more along the lines of what I was thinking, no hole to hole angle callout, this way to avoid stack up. But still looking for the proper way to indicate the segment (use a datum?)