I have a white background, on top of that a black vector shape (A), and a white vector shape on top (B). I have B on difference blend mode. My goal is that both shapes appear black, but that the area where B overlays A prints white. In case someone doubts, I'm using CMYK.
My problem is the following: the area I want to be printed white is light gray. If I set A to registration black it shows how I want it to be, but I have to print it, and part of A is shown. I don't know how to archive what I have in mind.
I know I could probably divide it into three basic shapes instead of using blend modes, but I would prefer doing it this way, so I can easily resize or move the shapes.