Dear Benjamin,
I’m not the one who developed this, but the WAMIT input files that NREL used to generate the 2nd-order WAMIT solution for the OC4-DeepCwind semisubmersible are available in my Aug 21, 2018 post in the following forum topic: Hydrodynamic analysis of OC3-Hywind spar buoy - #44 by Jason.Jonkman. The 6x6 mass matrix of the full system is given in the marin_semi.frc file as:
1.407E+07 0.000E+00 0.000E+00 0.000E+00 -1.392E+08 0.000E+00
0.000E+00 1.407E+07 0.000E+00 1.392E+08 0.000E+00 -1.448E+05
0.000E+00 0.000E+00 1.407E+07 0.000E+00 1.448E+05 0.000E+00
0.000E+00 1.392E+08 0.000E+00 1.270E+10 -1.094E-01 1.167E+07
-1.392E+08 0.000E+00 1.448E+05 -1.094E-01 1.269E+10 -1.953E+00
0.000E+00 -1.448E+05 0.000E+00 1.167E+07 -1.953E+00 1.229E+10
from which you can derive the mass (upper-left quadrant), center of mass (upper-right and lower-left quadrants), and inertias (lower-right quadrant) about the WAMIT reference point (0,0,0).
Best regards,