Zhann,
I was talking about the placement of the texture map on the object.
Having tried it for myself, (I just used a stock boolean object, and an old texture I had laying around), I can see the overlap in my own render. The solution as I see it would to be to give the painting/texture map a a larger border of white(or whatever the invisable mask color is), so that you can place it on the object better) and thus be able to fiddle around with the Y offset
and scale.
