moggiee
I don't have any figures however remember all the fuel was airborne.
As, say, 50k was offloaded from the tanker its burn would go down as the receiver's burn would go up. As it is a simple question of chemical energy conversion it depends who was burning the fuel more efficiently.
By filling the receiver to full you could also despatch an empty tanker back to Asi much earlier. For instance if the Vulcan had been filled to 50k and not 70k the tanker could have continued south for another hour (10k) and offloaded 30k to the Vulcan and would now need an extra 10k to get home. His buddy, either way, would continue with the Vulcan. On this sum the extra fuel required would have been 20k.
Also, if the tanker was sucking for 20 minutes, bucking etc, this would have 'wasted' 20 minutes bucking fuel and the time to prod.
If instead they had gone for lower uploads you might have 2 x 10 minutes of bucking fuel and 2 x prod manoeuvre too.
Lots of very deep questions which, with a year or two of trials Boscombe could probably come up with the definitive answer.