<<<
I agree with Jim, except I'll take that one step further on battery
sizing.  I subscribe to the Bob N school of thought that an alternator
failure shouldn't ruin your day or prevent you from going to your
intended destination.  >>>

Your proposal reminds me of the stoy about the guy who took off from somewhere in the deep South enroute to Texas in his light twin. Shortly after reaching cruise altitude one engine failed. He feathered  the prop and continued flying for another three hours before the second engine failed near his destination from overheating-- the ensuing crash killed all aboard.  What you propose is a violation of FAR 91.7, " The PIC shall discontinue the flight when unairworthy mechanical, electrical or structural conditions occur." If the alternator fails-- why did it fail? Is there a serious electrical short somehere you should be concerned about-- slowly burning up insulation and anything else it touches? Did the coupling or drive gear fail and an impending engine failure is just around the corner ? Remember SwissAir Flight 111? It was just a little electrical problem. Remember Alaska Air?-- just a little trim problem. Jeff Edwards
LIVP N619SJ