we use plain crosshair on centerline top and bottom. Illustrator 0.75 to 0.25 depending on the mesh.
Next thing I am about for our sim process is a hairline at 50% so we can actually see to line up the dots. I think on the high end prints we are registering to 3-5 thousands, with a halftone cross, I am hoping to get even closer.
think something like this:
i
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i
pierre