BN7 two-for-one battery swap

["Brashear, Jack, N" <JNBrashear@garverengineers.com>]

Hi All, I'm working on a BN7 (2-seater) for a friend.  Can anyone help
me out with How To Swap the two 6-volt batteries for one 12-volt??
Where to put it, what needs to be fabricated, how to secure it, etc..  I
feel certain this has been done before.  As always, thanks to this
awesome list.
Jack