It's true that only the Adagio from the 11th was recorded, so there's
nothing more "to get".

However, an excellent recording exists of the premiere of the 9th, with
Leonard Bernstein conducting, I believe, the American Symphony Orchestra.
The Diamond 9th is a very great work, given an extraordinary performance,
as I recall from the broadcast.  Securing rights to release this on CD
would not be cheap, but it would certainly be a gift to American music
in general.

John Proffitt
KUHF-FM Houston