Thanks! I think worst case I will try and "dumb it"

Who would you say is the "first marketing carrier" in my case? AC or CX?

3. Once the first marketing carrier is identified (through steps 1 and 2 above), it is the first marketing carrier’s policy to opt for the rules of the most significant marketing carrier (MSC) for the journey or retain the first marketing carrier’s own baggage policy.

Cathay Pacific opts to use the most significant carrier rules.