Ross Brawn has confirmed reports that Mercedes' 2012 F-duct will not be easily copied by rival teams.While Red Bull and Ferrari worked quickly to copy Sauber's clever exhaust solution, they are having difficulties over the Mercedes F-duct.Is it because they really believe it breaks the rules, or is the system simply difficult to copy?'SIMPLE AND CHEAP'Red Bull designer Adrian Newey was quoted by the O Estado de S.Paulo newspaper in Malaysia: "In regard to the aerodynamic (F) duct of the Mercedes, and sending the airflow from the back to the front, it is necessary to review the entire project."Mercedes team boss Brawn confirmed: "The opposition is so fierce (because) there's a recognition it's quite difficult to do."He rejected the rivals' arguments about cost, however, insisting Mercedes' system consists mainly of carbon tubing costing no more than thousands of pounds: "It's a very simple, cheap system, but not so easy to implement if you haven't integrated it into your car."This is at the heart of the frustration of some of our opponents. If someone could put it on their car easily, I promise you we wouldn't be having these discussions," he said.It emerged however, that despite the FIA having consistently sided with Mercedes on the F-duct issue, Lotus' technical boss James Allison has come up with two new arguments that will be put to Charlie Whiting next week in China.Brawn said: "We would obviously be extremely disappointed if someone was to take a different view."The FIA have been fairly consistent over their position so we have faith that they'll maintain that consistency."