Very funny, based on how it is written, FF does stack. All because you are not used to this or you believe it cannot does not mean it can't. It if the wording, good or bad, it can stack.
Secondly, FF does not state that it uses concentration. You only lose it if you lose concentration as if it were a spell. So i don't see how it can't stack with HM. if you can't look beyond the rules you put in your own head you can't see how it works. If they wanted it to take concentration it would explicitly say it, just like the spells, and they can correct that in the next book.
Secondly, FF does not state that it uses concentration. You only lose it if you lose concentration as if it were a spell. So i don't see how it can't stack with HM. if you can't look beyond the rules you put in your own head you can't see how it works. If they wanted it to take concentration it would explicitly say it, just like the spells, and they can correct that in the next book.