Does Serene Grace stack with King's Rock or Razor Fang?

Question

Serence grace is a weird ability it doubles Pokemon's addition effect of a move.
so I have a jirachi and it has the paraflinch set but it only gives 60% I wanted to increase it so I looked up items that increase flinch chance and I got kings rock and razor fang but some people say it doesn't increase some say it's either
60%(stays the same)
64%(serence grace lowers kings rock/razor fang percentage)
70%(kings rock/razor fang gives full percentage of 10%)
80(serence grace doubles the percent of the item chance including the move)
http://bulbapedia.bulbagarden.net/wiki/Serene_Grace_(Ability)
which one is the correct percentage if it's 60 or 64 I might as well not give it.
Thanks :D

Answer 1

The chance of flinching when using Iron Head would still be 60% with the flinching item. The flinching items only add the chance to moves that don't already have a chance to flinch, and since Iron Head already has a flinch chance, the item would do nothing.

If you use a different move that can't already flinch, Serene Grace increases the chance of King's Rock/ Razor Fang flinching to 20%. Up to you whether it's worth it or not. Most paraflinch sets just run Leftovers.

See the King's Rock box here for info on the items.