I've used the suggested fuel_flow_scalar   = 1.66 value from HvyEng on my last flight from Melbourne to Christchurch and must say that the fuel consumption now looks a lot better.

But the "Total Fuel Flow Indicator" doesn't represent the individual values of the engines, with or without the tweaked value.
It reads 17.000 while e. g. the individual gauges show around 24.000.