Very interesting topic, and as I am an absolute begginer, I can't help you with any valuable input but with some analogy you may find interesting.
I am currently in INARI, way North from the Polar Circle, in the heart of Lapland (the land of the Saami people). The Saami have a whole culture for knives, culture that developed and evolved during their whole existence in this harsh environment where a good knife at hand could make the diference between life and death. So, it is no surprise that for them, the knife has become almost a cult object. To cut it short is that here every Saami has a knife. Men have bigger knives, women and children smaller knives... maybe not unlike the Malay?
Please feel free to remove my posting if you think is unrelated to this subject.
PS: Could it be that the size of the keris is related also to the status of the owner?! The higher the status, the bigger the keris?