I am flying into MEL on QF030 ex LHR in First Class.

A couple of days later but on a separate PNR I'm flying up to SYD in economy.

I'll then pick-up my First itinerary again.

Does anyone here know if Qantas is able to link the PNRs in such a way that I won't get charged extra for the baggage allowance difference? (Which I understand to be 40kg/pax International First but only 23kg/pax Domestic Economy.)