From a 'recent' LHR-YVR flight on a 747-400 Roller engined flight...
Payload 38 tonnes
TOW 328 tonnes
Flight Time 8:58
Fuel Required 102.5 tonnes
Fuel Burn 89.6 tonnes
So, moderate weight, medium length flight = 70 tonnes below Max TOW and 10 tonnes per hour fuel burn.
Long live the QOTS