Tan,
I am fully aware of the viabilities ot tankering fuel, companies normally issue guidelines to Capt's regarding when & where it may be viable to tanker fuel, if they didn't then the Capt. may not be aware of contract fuel prices!
I don't know what science you're referring to but as a rule of thumb, it costs 3+% fuel burn per hour to carry that additional fuel thus it needs to be something like 20% cheaper in YHZ to make it viable on the sector concerned.