I built the Velleman transistor assisted ignition, and after sorting out a grounding problem, it's been great! Oddly, it solved a problem mentioned in the other thread, but not addressed here:
The bike's idle speed was on the high side, 1,400 to 1,800 rpm. A knowledgeable rider reported that switching from the orig. 6v generator system to a fully electronic 12v system by Powerdynamo enabled him to lower the idle speed. It has battery + coil ignition, so the generator shouldn't matter, but somehow it does.
When I fitted the trans ignition to my bike (and kept the orig. 6v generator and tiny 6 or 8amp battery) I was able to lower the idle speed to 1,250 rpm.
How, why, I don't know.