Agreed their diagram doesn’t make any sense after looking at actual 103 wiring diagram. And there’s no space for another coil in the magneto. Problem I ran into after taking brake lights out is kill switch wire (brown), new wire added for external coil, wire for points and shitty ignition coil wire all jammed in there started rubbing inside of the flywheel causing arching and shitty performance... so I ended up ordering another condenser (internal screw top) to keep all the wires secured nicely in there.
Have considered the possibility those “combo ignition coils” sold on treats are not actually “combo” in the sense of the original oem coils that come on the 103s. And if there were some way to wire in an external ht coil in conjunction with that treats coil maybe could get brake lights back .?.?.?.?.?