Called Cooler Master to ask about H100 mounting and they said:
"should be ok."
I feel that they are not basing this on exact product testing or customer feedback, but I read a lot of reviews of the H100 on Amazon and NewEgg and many people confirm that they are mounting it to the inside top of the HAF X case.
I am considering this same cooler for my HAF X or the H60. But, I don't know if the gains are worth paying for the larger cooler.