Red Bull Racing team principal Christian Horner believes all of Mercedes' rivals will now be forced to copy its DRS-assisted rear wing F-duct, now that the FIA has confirmed it is happy with the concept.

Although some of Mercedes' rivals were unsure about the legality of the device, which helps boost straight-line speed even more when DRS is activated, the FIA's Charlie Whiting said on Thursday there were no issues.

And Horner, whose Red Bull Racing team is already well advanced in developing its own version, thinks that all teams must now invest in working on similar projects.

"I think the intent of the regulation was to eliminate the use of F-ducts," said Horner when asked by AUTOSPORT about the rear wing situation. "If a team has found a creative solution to circumnavigate that rule, then it is ultimately down to the FIA.

"Inevitably if a team has found a route around, then it is a route that other teams will have to follow - and obviously there is cost involved in that. The question [of legality] is better proposed to the FIA than to us, and we are not totally aware of what the other teams are doing at the moment."

Mercedes team principal Ross Brawn said he had no doubts that the design was completely within the regulations.

"We have a system and we don't believe there is anything contentious about it," he said when asked about it by AUTOSPORT. "Whether we are the first or not the first to have such a system I don't know. But what the system is, I am not going to explain.

"We are very comfortable with what we are doing, and everyone is looking to push the boundaries all the time. We will see over the next few months how it develops, but if teams feel it is an attractive idea that we have got, then it will proliferate on other cars. We don't see it anywhere else, or they've concluded it is not worth having - but I am not going to say what it is."

Brawn also said there was no way that F-ducts could have been banned, because there is no official definition of what one is.

"It is not a debate," he said. "What is an F-duct? People talk about an F-duct but I don't actually know what an F-duct is. And if you ask the FIA what is an F-duct they don't know. So, what we are doing we are completely comfortable and we believe the FIA is happy with, so we will see."

Ferrari have never been shy about dumping an under performing (insert role here) on their ***, midseason if it has to be...

My guess is that they have bigger issues at hand currently (i.e. getting their car together so that Alonso can contend for the podium), and that once those are out of the way if Massa is still under-performing he will need to sharpen up his CV. And if it takes them too long to get their act together on the new car, Stefano Domenicali will be joining him.