Hi Mike G,
Let me rudely butt-in here. Please don't get angry, I just feel like I can add a little to the conversation.
There is a number of things you can do to any rotor system that will create or eliminate a particular vibration. I.E. pitch or depitch a blade (incidence) : bend trim tab(s) (if present) : Add weight at any number of points : Shift chordwise CG by leading/lagging a blade or shifting the entire head with shims. These are just a few. I'm sure some ships have many more. And...keep in mind, a perfectly-tracked rotor MAY NOT neccessarily be the SMOOTHEST rotor.
Each one of these VARIABLES, makes the data-point on the polar chart move in a different direction, when you make changes. EVERY AIRCRAFT IS DIFFERENT. The only way another person's chart can be used to balance YOUR aircraft is if the two aircraft have almost identical rotating and controlling parts.
The clock position readout for where a vibration is occurring doesn't have any relationship to the nose of the aircraft. It is related to where the accelerometer is mounted and where the photocell pickup is installed, and which blade has the reflective tape on it. You can install the accelerometer pointed ANY DIRECTION and install the photocell ANYWHERE as long as the reflective tape triggers it. Just be aware, your move lines on the polar charts will only be correct when these two devices are installed as they were when the charts were developed for YOUR aircraft.
Let's say you install the accelerometer up at the rotor head, pointing left, to measure lateral vibration. Then let's say you put the photocell about 12" in front of the mast, with a piece of reflective tape on one (master) blade.
Now say you built the ship from scratch and it's the only one that exists. Say you want to determine how adding or removing tip weight to the master blade makes the data point move. You can determine the azimuth of a move line on the polar chart by taking 2readings. One at rpm as-is, then plot it, then add tip weight to the master blade and plot it. That gives you move DIRECTION in relation to the accelerometer and photocell.
You can then plot intermediate points with different amounts of weight so that you end up with A) Move-Line Azimuth .and B) Weight/Distance Correlation.
This procedure can be done with each thing you have the capability to change on the rotor.
The concept to "take to the bank" here is... Your move lines and amounts of change per unit, ARE NOT GOING TO BE LIKE SOMEONE ELSE'S unless your ship is and exact twin of theirs and you have the accelerometer and photocell installed exactly like they did.