-Two is to add a backup battery next to the primary battery in the aft end of the baggage compartment.  I haven't quite figured out how I'd hook this up, since I'd really want it to be a completely separate power source (no alternator or connection to the other battery).  The Odyssey batteries are so very good that it could be charged on the ground periodically, and would be good when you needed it (hopefully never).  Still thinking about this, but it would mean adding 15 pounds in the baggage compartment, rather than 5 pounds in the tail.