9×9 {-1, +1} matrix of maximal determinant

Ratio of |Det R| to Barba bound: 0.848875

M=R^TR=R R^T:

9 5 1 1 1 1 1 1 1
5 9 1 1 1 1 1 1 1
1 1 9 1 1 1 1 1 1
1 1 1 9 1 1 1 1 1
1 1 1 1 9 1 1 1 1
1 1 1 1 1 9 1 1 1
1 1 1 1 1 1 9 1 1
1 1 1 1 1 1 1 9 1
1 1 1 1 1 1 1 1 9

R:

+--------
-+-------
--+++----
--+----++
--+--++--
----+-+-+
----++-+-
---+--++-
---+-+--+

Notes:

1. Cannot achieve Barba bound as 17=2×9-1 is not a perfect square.
2. Reported to be maximal in [EZ].
3. R is unique up to equivalence [Sm].