The SWB offset arm works best if your rudder clevis attach points are slightly aft or forward of the rudder hinge line. If the clevises attach to the rudder horns directly in line with the hinge line then an offset arm should not be used. The offset arm also works best if the cables are installed in parellel, and not crossed. As far as rubbing is concerned it is absolutely no big deal to file out the slots if needed to eliminate any rubbing. I don't believe I have seen a plane yet where the slots were where they needed to be.