Is there any way to control the PM alternator?  In other words, can you turn
it off?  Say you add one of these as a backup, and your normal alt is an ND or some
other type that can be turned on and off.  As a part of pre-flight, you
could turn off the main alt, and verify that you still had charging voltage,
but would you ever be able to turn off the PM alt and verify that your main
alt was working?  With the type of voltage alarm that many of us use, I
don't think you'd get a warning unless both alts were down.  Cheers,
Rusty (I still like it though)