Qantas Frequent Flyer - Best LHR-SYD route for upgrades

Does anyone know if QF2 is regularly full in J class at the moment? I'm going LHR-SYD in a couple of weeks and I'm trying to figure out whether travelling via BKK instead of Sing will increase my chances of getting an upgrade. I came via Singapore 2 weeks ago and it was jammed (on the A380) so poor me had to put up with PE.

BKK and HKG are much less busy than SIN (not surprising as SIN is a mini-hub for QF while BKK and HKG are not). Personally I would pick via HKG as it is nicer flight and airport than BKK and some chance of a free seat upgrade.