Ron:

I like your scheme.  I really like the one-plug to ship's power
solution.  The APC case looks like a nifty piece of gear.  Are you
thinking you would keep the laptop in the case while it's running?  I'm
wondering whether it will get sufficient cooling air.  Also, regarding
putting the antennas on the glare shield, the WxWorx antenna and the
mouse GPS that I have (and all the other mouse GPSes I looked at) have
an amazingly strong magnet in their base.  I would worry about how they
might affect the whiskey compass and possibly other instruments/avionics
(I'm no electronics expert!).  I put mine on the hat shelf at the back
of the baggage area using Velcro.  Reception was fine (my built-in GPS
antenna is behind the baggage bulkhead on a phenolic pad glassed on to
the inner fuselage, installed and tested by a top avionics shop).

Lee