Disston, I share your thoughts exactly, though my old advance was pitted and I think it was causing the old points to close rapidly due to the wear on the rubbing block.
I did read Duane's article, and I was hoping that uneven wear on the two lobes on the advance was causing the split image, but it appears it is not. I would have thought the camshaft tip had runout (I don't have a dial gauge to measure this yet), but then the image was corrected with new points. And now it's back to acting strange. The only explanation I can think of for the points is that the pitting that develops somehow causes the points to fire at different times every half revolution or so. Or maybe the pitting causes issues with possibly weak coils, and/or corrosion at the cap/plug contact.
The funny thing is it starts and idles fine, always returning to a steady 1000rpm, and never any misfires at idle. So yes, the problem is still cutting out at speed, I think I'll ride it some more to see where it stands now.
Any word on the slight out of tolerance of my secondary coil? 6.68 and 6.73k ohms instead of 7.5-9.15k. I thought the failure mode is that the secondary coil would break and the resistance rise or become an open circuit, but maybe not? Oh I completely forgot to mention: the tachometer needle tends to weave back and forth at my cruising engine speed of 3.8-4.2krpm (where most the stumbling occurs), not erratically, perhaps back and forth twice a second or so. Amplitude is about that same range (3.8-4.2krpm) I don't think it does it at other speeds, but then again I don't usually look at my tach unless I'm cruising.
I'm hoping the local airhead tech has some spare coils I can try without having to buy a new set only to find that it was something else in the ignition or fuel delivery.