Hi Bob,
FWIW: Always two (2) sides to every opinion on any Forum ...... pick & choose is the way to proceed.
1. Had a newly installed malfunctioning Model A starter switch that refused to disconnect, thus the starter continued to turn with the engine running. Disconnected my new keyed cut-off switch and all was well.
2. Not a big deal, but as far as my luck, with a wedding party looking at us, my son was getting in my Model A to be driven to his wedding reception with his new wife.
3. Another experience, but not Model A:
A. I have a cut-off switch on my vintage Farmall tractor.
B. Had it parked immediately adjacent to my house idling when the engine vibrations caused the steel starter switch rod for the pull switch to become unattached and fall on the starter/battery live connection covered with old oil & grease.
C. In seconds, flames were 18" tall touching the bottom of the metal tractor gas tank immediately above.
D. In about (5) seconds I was able to turn off the battery ground wire's cut-off battery switch and possibly save a tractor and a house with my wife & dogs inside.
E. Could have been a very sad story.
But, I did not get a fire extinguisher for my Model A "yet" !!!!!