Finished the truss rod groove ends at the the headstock side of the neck.
A small alignment error occurred between the center line of the neck and the truss rod grooves, the headstock veneer is also not optimal aligned but has a deviation in the other direction , which means the deviation adds up.
In total it's only 2 millimeters off center, I think it's more important that the the truss rod covers are properly aligned with the headstock veneer and decided for a off-center solution.
Once the fingerboard is in place no one will see it, and because I went for a double truss rod the exact center alignment for these two is also not that critical.