I have no idea about the Bs point ignition but want to understand your issue 😉
Is the adjustable range of the ground plate not sufficient?
I’ve found an instruction in a german language manual. Here is the very brief version of it:
-first set the points contact gap
-second set the ground plate position
-third check timing with stroboscope or electrical angle measurement unit (?), no idea if that is the correct word 😉
Attached two pictures related to first and second. Pictures file names are for the order, not related to B model numbering.
To get it more confusing there are numbers on the pictures themselves 😉