Tracking testing is done. I did some measuring also. The way the hitch is on the bike, namely, has the trailer center line 2" to the left of the bike. Aside from that, the tracking is not crabbing to either side that I can tell. It is a bit hard to tell with the lack of rock solid stability in the bike tracking/leaning while I am riding it. I had someone get a couple videos from the back while I tried to keep the set up as straight as I could for a short distance. All seems well enough there. The only tracking issue that bothers me is the 2" to the left - which I've known since I made the rigid hitch (in place of the OEM rubber spring rod hitch doohicky thingamajigger).
I am not sure how to dial in the tracking. Without changing the hitch on the bike, the change would have to be in the tongue bar on the bike. If I try to take out 2" of "width" without changing the geometry much that would bring the front of the trailer closer to the bike. I suppose I may be able to offset the bar, though. That would also require a rather significant change to get the parts to do that (new bar, but as discussed before - the OEM one is pretty thin anyway so it has been in the back of my mind to replace it - this might give me a reason to do that).