Thanks for the comments.
Kronckew, I wish I could give a better answer but I really am not sure. These areas are fairly "scrubby" without a lot of major hardwood trees. I have read before in the Sahel regions the wood warps quite often so I guess they replaced the shafts fairly frequently.
I found this image on the forum which shows a pretty similar spear fully mounted. You can see there would be a small iron counterweight but really quite simple without the big butt spikes other Sahel spears have.