So, ten minutes of reading about resistors and I'm ready to electrocute myself, if only I knew how.
This is about the simplest explanation of how resistors affect voltage I could find and I still have no idea what they're talking about -
I'm so glad I decided to run a (nominally) zero resistance wire to my coil and give it 12 volts under all conditions.
The reason I've got myself in a tizzy about this is that when my midget developed a misfire I noticed that the coil was getting red hot, so replaced it with a non-ballast 12v one as I didn't realise I had a ballast resistor in the circuit.
First run out after fitting it the misfire had gone and the car ran fine suggesting the old coil was on the way out, but at the end of a 30 mile trip to the coast the engine conked out as I pulled on to my driveway and wouldn't restart.
After a bit of investigation I replaced the coil with a ballast coil but still no spark, then I took out the fancy electronic ignition module and put the points back in and it ran. A bit of research revealed that the electronic ignition module probably failed because of the wrong voltage going to it.
By then I had already committed to electronic ignition on my Speedster's engine and I don't want to burn it out by under or overpowering it. At least now I know that it's connected in accordance with the manufacturer's instructions so it shouldn't fail.