Maybe some clearance already.
The picture from the recommended shop site does say, this referred CDI system does use the "Automatic advance angle ignition".


Does anybody know the figures, or where to find the curve shown at a diagram ?


I have heard about something like 5° retard directly at the beginning, than another 20° retard until 500 u/min and than it will change direction in to full advance, archiving it by 1000 u/min.
The situation here, 9 sparks/tripped magnets at one rotation does change it dramatically, because this maybe will confuse the electronics and the bits and bites.

This picture is from the shop site.
https://www.cad-modelltechnik-jung.de/bauplaene-modellmotore.html
It does show the distributor disc  situation and the the bracket with the carbon brush and lower of it the hall sensor.
The black disc is made from POM, Delrin or similar isolating material. Inside, as an inlay, the 9 copper slider which are temporary in contact with the carbon brush.
Each slider is connected with one single spark by a static wire.
Inside this, is a Aluminium disc, hosting the 9 magnets for the hall sensor.
This disc is adjustable assembled with the POM disc for ignition timing.
Firing order is 1-3-5-7-9-2-4-6 from front view.
I have heard about this advance/retard curves already, but I do not know if this RCEXL CDI ignition system is equipped with it also.
The timing recommendation is 5° before TDC, later may be up to 11° possible.
If I am right, a normal 1 cylinder RC flight engines are there more aggressive with up 28° and more.
So if the above mentioned curve is available here and if it will affect in any way this timing set up, no idea.

And yes, my brain does fight with this rotating crank case and the fixed crank shaft, too.

Thanks Andy : I haven't got any photo of boring my Major cylinder, so long ago that it predated waving any sort of digital camera at it ...  I seem to remember setting it up for between centres machining on the Myford boring table.  Made up a fairly hefty Geo. H. Thomas adjustable boring bar, which has been useful for the Quorn and at other times. 
  As it looks like a week of mostly rain ahead of us in Southern England, and not much good for other than indoor activities, I will have a go at getting my Major Beam finally assembled, at immensely long last!.  Been doing a few of the last drips and drabs of left over jobs, pipe bending and brazing flanges, making the curved crank well trough.  'Spect that I'll find a few more overlooked oddments to need to attend to while building, a few things that need measuring off from the components in situ, or the odd stud and nut that has gone AWOL.   Dave

Sorry for the late reply Kim. I missed the link going "above" the pivot point, I will go stand in the corner.
Congrats on a very fine model overall.
Ian.

From the description there are 9 separate pins connected to 9 separate spark plugs, when the cdi is tripped the spark will only travel to the plug who's pin is making contact.

So 1st revolution of the crank it fires the correct cylinder, second revolution it will fire that same cylinder but as it is not on the compression stroke the spark will just be wasted.

With 9 magnets it will get tripped 9 times per crank revolution but as only 1 plug in turn is connected the other 8 sparks will just go to their respective cylinders

No chance of the wrong cylinder getting the wasted spark.