RE: Minimum Battery Voltage
No test data on starting but some empirical data on minimum to run.  Some
years back my WBX '90 Westy died coming out of Borego Springs.  Got to the
side of the road and immediately checked my engine battery, 8.8 volts. So
that seems to be about the minimum that will keep the engine running.

BTW, I had not had a red alternator light!  Jumped to my big aux battery
and continued to my brother in laws place outside of San Diego, replaced
the regulator/brush pack on the alternator and all was well.  I now have a
volt meter on the dash, if that happens again I should be able to catch it
before I have a dead battery.