Posted for "John Barrett" <2thman@olympus.net>:

Most IVP builders I know are using a dual electrical system with a X-feed
capability for engine start and for emergency operations if one fails.  One
alternator will provide power depending on your load requirements, but a
second makes sense to me even if it's a small one for true emergencies.  Two
batteries are a must - SLA - 20 Amphours is my choice.
Bob Nuckolls (sp) is the source for this thinking.  I'm  having my panel
done by Aerotronics in Billings, MT and they will have some refinements to
make/suggest concerning this approach.

The Jet 2 1/4" peanut gyro is guaranteed to keep giving useful information
for 9 minutes after power is lost.  In practice, it's said to go for 20
minutes if you don't put G's on the airplane during the wind down time.
Using that as a backup to an SFS EFIS might provide the peace of mind you
need.  Works for me.