I now use a booster box. No reason not too, once you get the thing working right. I wouldn't put the box on till I had the points working right though.
It sounds more like you have the slight variation of bouncing points that aren't really stable. It sounds like it, I can't be sure. If you are getting one solid mark above idle it's OK. A little jumping around idle can be normal. Or so one of the Gurus told me when I had this problem.
Another test I think is how the bike runs. A smooth running BMW has an even firing engine. When My Beemer had the double timing image it had a lopey idle. It almost sounded like a Harley. Almost, but not quit.
It's true that Duane mentions changing advance units as one way to sometimes eliminate a double image. My experience with that was it made no difference and I had about 5 advance units to go though. You have read Duane's articles on this problem?
Another inmate here recently was able to measure the run out of the cam tip with a dial gauge. Set this to zero and thereby eliminate a double image.
Not sure any of this is about your main concern. The problem is still intermittent cutting out at speed?