Hi Padraic, I think the right way to do what you are trying is to write an engraver that listens for slur events and alters the spacing of the music. (I would write one if I could, but I'm not at that level yet.)
Until you have one I think you can solve the problem with your own hack, where unwanted slurs are appearing, with \omit Slur. Does that work for you? Kevin
