How to set PID for Tracking service?

OK, I'm getting a bit closer on Tracking with my InMoov head.  Had to do a bunch of clean up here and there but have the head back together and mounted on my new stand with the neck piston servo in the mix so I have X and Y axis movement.

I've slowed the Velocity down from the -1 max setting to see if that helps but it didn't make a big difference.

It is almost tracking objects but seems to wander a bit and then loses the object.  I've been trying to figure out how to set the PID values.

Using the latest MRL 1.0.2000 that I downloaded a few days ago. 

When the tracker service starts I have a tab and in that there is a default Kp 20.0 Ki 5.0 and Kd 0.1 with set pid, invert, input output and compute blocks.  I have tried changing the p i and d values and clicking on set pid but that doesn't appear to do anything.  I've tried doing setPID(5.0, 1.0, 0.1) in the tracker.x and tracker.y services in the script and didn't see any errors in the log, or at the bottom status bar.  But this also didn't seem to make any difference. Edit: I guess I didn't actualy try setPID() since when I checked the file the setPID lines were missing, so probably got overwritten since I had made that change in an external editor.  In any case there is no setPID() method on the tracker.x and .y..

So what is the correct way to set the PID values and have them stick?  And how is the tab set pid, invert and compute supposed to be used.

Is there some documentation for this that I haven't located yet?