disston, this troubles me too, and I was especially confused when it went away when the points were replaced, and not when the advance unit was replaced. Then I was frustrated when it was back last time I checked. Yes, just ordinary points. I read all I could about double images.
Here's what I see: at idle, there is a double image, though it's hard to tell exactly where either image is. The separation appears to be maybe 3mm. Just off idle, the image sort of gets clearer, the double S and lines get clear, become just one image. Then the dot comes into view just before 3krpm and becomes centered in the window, but it's not as solid as the S was as it was 'leaving'. When I timed it in Grand Rapids just before the final leg, I saw a 'ghost' dot pass through the window before another dot became centered at full advance.. separation maybe greater than 10-15mm. Which worried me greatly and is why I retarded it until (I think) only the ghost dot becomes centered. That's the best I can describe it, it's hard to tell exactly what's going on. I wonder if I could find a non-inductive timing light that hooks up to the points to see if I get the same result.
And that's also why I was leaning towards an ignition issue, but I have no idea why it's intermittent when I have observed the same timing effect in the past and the bike ran perfectly for long trip(s). I should mention that after 1500 miles, the new points have already started pitting a little, forming a mountain and valley, though not as pronounced as the previous set. Again, the condenser was replaced with the points. Is this normal progression?