The stencil was designed using the ref_pattern.csv point configuration.
It can be 3D printed with PLA with 15% infill and 0.2 mm layer height. The model might need to be scaled a bit in order to perfectly fit the ball. The ball diameter is indeed different depending on the manufacturer and the stencil needs to be a tight fit for the ball not to rotate inside when you are drawing the dots. The scaling can easily be done in the slicer software you are using.