Just to add a little, the 1 per rev experienced by the pilot is also due to the mass distribution of the entire rotor system, mostly whether the center of mass is or is not on the axis of rotation.
Vertical hop could mean a lot of things, so I'd be very cautious using it. The vibrations will be dominant in either the vertical or in the lateral plane. For the pilot, the direction doesn't normally make the job any more difficult or uncomfortable, but it is important to know the direction for reducing the vibrations.
If you haven't yet noticed the difference on your seat between the 1per and the Nper, you can normally feel the Nper get worse at high blade pitch settings and high forward speed. 1per is not as easy to produce, but if you feel a vibration during an autorotation that is slower than the Nper (1/N of the frequency) then it might be the 1per vibration.
One problem with learning to feel which are the dominant frequencies, is there are many frequencies throughout the system, some of which lie very close together. For example, a 1per on the tail can be very close to the Nper on the head, especially for larger helicopters (N>=5). Also, frequencies can couple in ways that are difficult to imagine.
Matthew.