Haven't read the whole thread but:
Originally Posted by Flightpathobn
As an example, the Vref CAT C for a 737 is based on 40T LW with flaps 30...
The pilot must calc actual LW and flaps to determine to use the CAT C or CAT D approach...
That's not what the Australian AIP (ENR 1.5 1.2.1) says at all. The approach CAT is determined by the Vref at MLW in the approach config. You cannot reduce the Cat here because you are light.