I'd say 7. He already fought dwo grand magus' at once so even that is more formidable will not be that much of a difference.Granted he can't use twik as an armour.
i would give it a 5-6. Emery isn't completely healed for one, which may exacerbate the situation, but his transformation alone is able to fight GMs. So, not easy by any stretch, but Emery can hold his own.