"To prove it, he tracked down a Toa of Fire and a Toa of Earth and blasted them just as they were merging their forms. " - BIONICLE: Dark Hunters
This makes it sound like they were forming a "Kaita" of two Toa. Is this correct? We never heard of this outside Prototype's story. Previously you have also stated this to not be possible:
5) So, the minimu for a fusion is 3? (For a Toa at least)
2) For a voluntary fusion, yes. Spear of Fusion could merge two Toa.