Just some real world experience, for what it's worth.

Lee,

 

You are correct.  'Tis bad to be marginal. 

 

The question is "Which equipment will go off-line or recycle if the voltage drops too low?" 

 

Some time back I had a marginal wire size to my essential bus (VM system is one item on that bus) and, over time, I added/changed electrical equipment (i.e. Terra (5W) -> Garmin 430(10W)) that resulted in a somewhat higher load - - So, with the lights on, the xpdr blipping, flaps in motion and a gear system blip, the voltage would momentarily drop below 7-8 volts (after the bus isolation diode dropped it by .7).  That was just enough to recycle the engine monitor, including it's flight timer.  Heavier gauge re-wiring of the bus interconnections and Essential bus to battery line has fixed that problem. 

 

Rob,

 

Anything that's worth adding is probably electric - Go with the 60 A alternator and make sure inter-bus wiring is capable of handling a load greater than your first flight design.