Interesting questions Neo. I have no conclusive evidence on this subject either, though in spite of the use of the word hulu (head) to describe the keris hilt i am not so sure that the character of the hilt rules or directs the attributes of the blade so directly.
The hilt is the public face of the keris though. When a keris was worn in public the blades were not made visible to others on most occasions. I fearsome face on a hilt was most probably meant to keep negative forces away from the keris and it's owner, not a reflection of the nature of that particular keris.
