The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  X
 0  X  0  0  0  X  X  X  0  0  0  X  X
 0  0  X  0  X  X  X  0  0  0  X  X  0
 0  0  0  X  X  0  X  X  0  X  X  0  0

generates a code of length 13 over Z2[X]/(X^2) who´s minimum homogenous weight is 12.

Homogenous weight enumerator: w(x)=1x^0+18x^12+8x^14+4x^16+1x^24

The gray image is a linear code over GF(2) with n=26, k=5 and d=12.
As d=12 is an upper bound for linear (26,5,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 5.
This code was found by Heurico 1.16 in 0.000403 seconds.