Experience helps in sorting out the tracking. I had plenty of experience with my old Kyosho EP Concept, and its stock foam blades. I even added additional tip weights to make eVoyager blades work on my EP Concept ! It would track only at a given rpm, go up or down and the tracking would shift. On my Trex, I only had the stock servo linkage system for about two weeks before I got frustrated with all the slop. My friend( ie more experience) had mod'd his Trex to eCCPM.I modified mine, and wow what a difference. Hovering in one spot was so much easier. Tracking seemed more consistent. Since then I've always used a DIY eCCPM set up on my Trex. ( the down side of eCCPM for me is in a crash. I typically strip a servo gear, HS56) So far tracking has not been a problem. I then experimented with the dampening. I wrapped teflon plumbing tape over the orings to tighten it up. I thought the cyclic response got crisper. Still no tracking issues. I then put two washers over the feathering shaft on either side of the head. The OD of the washer was an exact fit to the ID of the head. This made my head rock solid, no dampening except for the flexing of the stock head. Still no tracking issues, but I had a problem that at first I thought was a tracking related problem. At a certain head speed, the heli would start to oscillate, ie wobble. After getting bored with this set up, I went back to teflon tape over the orings, and removed the washers. No more wobble. The other one, was inconsistent tracking, the tracking would shift slightly with rpm, seems that my problem was typically due to a poorly balanced blade or a flybar paddle that was out of alignment. Basically, what I am trying to babble is to experiment, and to ask for help and to experiment some more.
Forgot one more detail, some people have mentioned that the bolt tightness of the main rotor grip can affect tracking and more so, lag-lead vibration.