Previous 27×27 {-1, +1} matrix of largest known determinant

Ratio of |Det R| to Ehlich bound: 0.956639

M=R^TR=R R^T:

27  3  3  3  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3 27  3  3  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3 27  3  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3 27  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3  3 27  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3  3  3 27  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3  3  3  3 27  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3  3  3  3  3 27  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 3  3  3  3  3  3  3  3 27 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 27  3  3  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3 27  3  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3 27  3  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3 27  3  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3 27  3  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3  3 27  3  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3  3  3 27  3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3  3  3  3 27 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 27  3  3  3  3  3 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3 27  3  3  3  3 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3 27  3  3  3 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3 27  3  3 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3 27  3 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3  3  3 27 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 27  3  3  3
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3 27  3  3
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3 27  3
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  3  3  3 27

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

Notes:

1. This matrix has been surpassed by a new record.
2. This matrix was discovered by Will Orrick and Bruce Solomon on 20 January 2004 by hill-climbing from a maximal 25×25 determinant augmented with two random rows and columns.
3. It surpassed the previous record.
4. Ehlich bound is not achievable as it is not an integer.