Hi Walter,
Thanks for the great reply. We were planning on doing these measurements.
As we don't do the shot peening in house we don't actually know what they are doing. I will ask the saturation curves.
The drawing asks for a coverage of 2.0, what they actually apply is unknown for the moment for me. Could this be the cause of being out of dimension (hole becoming too big)?

We will need to analyze further, but knowing we might have to look at their coverage would already help us a great deal.
Best regards