Hy Stoyo, I discoverd that Our customer do not want to see shadows because he think the shadows on arrows are the reason of another strange effect...
Despite I do not know how he think that the shadows and the strange effect are related to....Anyway, the strange effect is what follows:
when the "pasted" image is printed on some ( not all) printing machines, the arrows appears surrounded by a filled gray rectangle..... so the behaviour of the chart look like a patchwork of gray rectangles.

.... the rectangle corners are at the two end of each arrow.
I try to see if there is a rectangle around the arrows ( i.e. a near blank rectangle, invisile at human eye) but nothing at all!!!When I look at the document on my system I see that all pixels around the arrows are white ( 255,255,255 in r,g,b format)
Could it be that on certain systems colors are remapped?
again I don't know how to think.... ???
Thank you
Franco