I was going to say that you could put the AMF on one of the huge caster's corners (much like occurs with a Medium creature), but since AMF states it is "centered on you," that would seem to preclude that (though it still will be centered on an intersection within the huge creature's area; as a 10-ft radius, there would be 2 two-square sections that emerge from the huge creature).
What I'll probably allow is for multiple people to get in on the grapple, such that they can completely cover the Klurichir in AMF's.
The other option for a Huge caster, of course, is a Widened AMF, as a 9th level arcane spell. Then it would be a 20-foot radius emanation.