From what I can see, the angle of a spotlight seems to be 60 degrees no matter what. I'm not entirely sure what the attenuation parametres are based on. Based on this I've built a 14-pointed arrangement of them where they are placed at the vertices of a dodecahedron (20-sided pythagorean solid). This completely minimises the overlap which, despite the numbers given for the angles, don't seem to have anything to do with the actual angle of the cast light. Why? Because at 160 degrees (the default angle limit), almost half a sphere would be lit -- but isn't. Further, it would make sense that if the angle really described the angle of the light, then upping the limit to 360 and setting it there would then create almost a real omni. But that hasn't worked at all.