Ok, I tried this to the best of my understanding, and I am not getting the results I am looking for. Aside from the sharp edges of the spots which intersect (am I placing the wrong? Should I have more than 4 for best coverage?), I don't get the falloff in corners and I get artificially lit furniture insides. But, it does run faster (with 8 additional lights, only half of which cast shadows, the render took only 7 min), so maybe there is a way to set these lights in a more natural way? (I used brownish lights on the flooe - eventually the floor will be brown wood, and light grayish blue for the top ones.)