Casey Stoner isnt underestimating the task ahead of him if he is to end Valentino Rossis seven-race win streak at the Italian’s home grand prix – and hand Ducati a long awaited Mugello victory on Sunday. We know Valentino is fast, hes won so many times here. Last year we gave it out best, but it wasnt good enough, said Stoner, who lost out to Rossi by 2.2sec last season. Valentino is going to be …