Hallo there Dan!
I'm not very much into handling stone axes, for that I have made just one (but I'm preparing the second, I have crafted the axe and am now preparing the handle.... a set of picture will soon appear here
).
But I've seen many of these axes, and I've come to a conclusion: the "conic hole" is the best way to handle it, but I suggest you not to pierce the whole handle.
I mean, "dig" the handle, but leave some wood intact, so that the axe will stay there, when you use it.
I'm sorry for my poor English, I don't know if you have understood, but as I said I'm preparing a handle and I'll post a picture that will explain exactly what I mean!
Greetings,
Mauro.