Orientation of mass moment of inertia

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I think i get it now. To do what i want to I guess you have to:

First make sure where you initial reference frame is of the link. If you imported an stl or dae file this is the origo of you drawing.

Next find out where the COM is located acoording to this initial reference frame and use this in the link sdf under pose under xyz.

Then align the inertia axis as you wish and rotate them using the rpy of the same pose parameter.

You now have placed the COM according relative to the link reference frame and aligned the axis of the inertia matrix.

Now enter the inertia matrix according to the axis and through the COM. Link to example

Please note that the pose parameter is under the inertial parameter and this denotes the position of the COM relative to the link reference frame and that the rpy denotes the orientation of the inertia matrix.

Hope this helps someone else.