I guess in my case, it could be that the headset isn't fully vertical when I'm wearing it, even though the fit is good, sweet spot in the right place, etc - everyone's face is a different shape after all.
In SteamVR, when I'm not using the hand controllers, the blue dot cursor is also a little high. I'm not aware of any way of correcting for this, but perhaps it's a general VR issue rather than a specific Apache one.
If anyone has any ideas, or is aware of some way of correcting for this, I'd be happy to give it a try.