What you are doing looks plausible, but a concrete runable example would be helpful. In what you show, the only thing I would be concerned about is that one edge of your wedge is on the x=0 plane, and if your model is also based on the x=0 plane then you could have a Z-fighting problem of some kind. (A Z-fighting problem is, in this case, where you subtract B from A, and they have a face in the same place so the program can't quite figure out whether it's not there, or is there but is zero thickness.) The normal solution to such a problem is to shift the "negative" object just a little so that there's no ambiguity.