Respectfully, I would check very carefully that your Ops Manual states what your duties and responsibilities are, and then consider whether you have had enough (any?) training for this 'safety pilot' role...
If not, and the company say that you're just there to do a Cat 3 landing if the need arises, do the sensible thing and sit in the cabin drinking tea until you're called for.
IMHO, having professionals in the flight deck to carry out undefined roles for which they have not been trained is a recipe for trouble, and I'd not be part of it (that said, I'm never likely to be).