I read Duane's page long ago, but didn't have the balls to try it.
But I just went out and measured my point gap at both lobes of the advance, and sure enough one was tighter. My points (which, by the way, are made in China...) seem to angle towards each other just a little, so I could tell based on how far the feeler gauge slid in before it encountered the slightest resistance.
Got out my punch and hammer and tried Duane's method.. and I seem to have the point gap now equalized, but my double timing issue is still occurring. It's funny though, the region between idle and full advance seems to be steady - i.e. as the S idle marks leave, they become one image (and the sound of the engine changes, it seems to get more even), and as the full advance dot comes into view it's also steady and one image, then it becomes dull and two images, about 10-15mm apart. Maybe one the pins that control the stop and start position is bent?
So.. I think I'll try swapping back my old advance with pitted lobes and see if anything changes.
I'm liking the idea of an alternator-mounted electronic ignition so there's no way there can be a double image, and I can leave the points in place in case it fails, so swapping back on the road would be easy. Maybe it's time just to bite the bullet. But what if it's somehow my coils? ergggg