Is your question request related to a problem? Please describe.
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Describe the theory or implementation approach that you have a question
I am want to understand how to correctly prepare the geometry and set Inertia values.

Personal project context
I try to model floating ship that consists of different parts. I want to use hydrodynamic body for floating part and non-hydrodynamic bodies for non-submerged parts. I created the geometry (.stl mesh files) for each of the ship part, but I am not clear how to set the Inertia in WEC-Sim input file.
The problem is that WEC-Sim requires input of 3x1 inertia matrix. Therefore these inertia terms are principal moments, right? Can WEC-Sim automatically calculate the direction of principal axes? This is important because geometry of ship parts in .stl file is oriented directly to the final position that should be on the ship. In such a case principal axes are not aligned with global axes during import (see Figure), but terms of Inertia in WEc-Sim called Ixx Iyy and Izz (not Ip1, Ip2, Ip3).

Should I rotate the parts in CAD so that the principal axes correspond to the global axes and only after that import the .stl file and manually change the orientation of the bodies already in WEC-Sim?

Describe the type of conclusion or resolution you are looking for
I would appreciate if you will explain how to prepare geometry or how to set inertia 3x1 matrix for the case if principal axes of the body in .stl file are not aligned along the global axes.

Additional context