When most folks refer to the ear hole (external auditory meatus), they are referring to the soft tissue ear hole and not the boney ear hole which is actually lower down on the skull.
The problem with ear shots is that if you are just a tad high, you end up skipping over the top of the skull. Slightly below behind, underneath, or forward should work very well.
The true "sweet spot" is just behind the ear. It is where the brain stem connects to the spinal cord.
It does work well, but isn't where the brain stem connects with the spinal chord. Directly behind the ear puts you either in neck muscle or hitting the occiptal. It does work, but does so without directly having the brain stem or spinal chord hit.