Games : Flinch chance rises?

I plan to raise a Togekiss with Serene Grace. Togekiss can learn Air Slash which has a 30% chance of making the opponent flinch. I read from Serebii that Serene Grace doubles the chance of the secondary effect occuring, which would make the flinch chance 60%. If I make the Togekiss hold a Razor Fang, which increases flinch chance by 11.7%, will the chance of flinching become 71.7%? Or is Razor Fang's flinching buff also doubled by Serene Grace, making the overall flinch rate 83.4%?