Arjan,
On Steller's sea cow he doesn't claim that mine are that, only sea cow. The dugong, the one of the living species closest to Steller's, is found outside Borneo.
I am not a "hilt-material guy" myself so I will probably put you into contact with one that is and then it would be interesting to read your conclusions.
Your words "animistic Dayak" reminded me of an idea I got when he first told me about it being sea cow (Alan, please don't read this because I am speculating based on documented folklore from neighbouring places
)
If you are in the forest you want to have hilt material made from wood or a forest animal not to disturb the ruler of the forest. But if you are planning to join a pirate trip on the sea the ruler of the sea would be very angry if you had a hilt from a land based animal on your sword and ship (wood seems to be neutral being found both in the forest and drifting around on the sea).
This corresponds to the beliefs of the Malay fishermen who even had a special language to avoid mentioning land based animals when on the sea not to disturb the ruler of the sea. One version is the one studied (Annandale 1903) in Patani and Pahang where for instance a horse was renamed chehweh dras (= fishing language prefix + fast) and a buddhist monk chehweh kuning (prefix + yellow).
Michael