Ah yes, I should have replied earlier, but was miles away at my Dad's.
How big are the holes through the middle?
A normal loop knot on the hair is usually tight on my wooden balls. (Oh er!)
I often tie on a meshed pop up to the hair loop end, it holds the ball in place.
If bigger, a piece of braid pulled through, knot the two ends together tightly leaving extra as a tag end and you can attach it to the hair loop, or even rig ring on the shank.