I wouldn't use both DC's in a CD - Cover role, they'll leave too much room in front of them. I'm unaware of their stats off the top of my head, but one of them needs to be a stopper. If none has high enough bravery and aggression for the role, then I'd recommend Ryan Shawcross or Andrea Ranoccia or even Lucio, he remains great up till 2014 at least.