I think its in QF's interests to string you along as far as possible.
It might be instructive to calculate how much "back pay" Qantas accumulates every week they can keep you on a lower rate, and more importantly, the interest on that back pay each week - which I expect you don't receive.
My guess would be that it is in QF's interest to delay any settlement for as long as is humanly possible...ie: until you all get up to walk out the door.
Assume cost of funds = 6% pa
Say 2000 Lames at an average of $80K all up per year.
Thats 2000 X 80,000 X 3% = 4.8 million but of course thats a full year
Interest on half of that at 6% is $144,000 that Qantas has saved by delaying settlement with you (less consultants fees) .
I'm sure PAF will be only to happy to get out his calculator and do the proper compound interest calculation for you to get an exact answer.
You might also like to think of the tax implications of receiving such a lump sum as well.