Hey Rusty, How are they hangin' old fruit,
From my expereince with other helos and limited time on teh 139 I'd take a wirld guess and say if you allow either a 5kt reduction in TAS or a 5% increase in F/F you can't go too far from reality. Given that you nprmally plan on around 450kg/hr but in reality at your LR cruise config you are around 400ish kg/hr, that would mean around an extra 20-25kg/hr if you maintain the same cruise TAS as normal..........just a wild guess
cheers