Did you add a little dish soap to cut the grease faster, or just stick with the vinegar mix?

Man, that hits home. Ran a 6010 root on some 6 inch sch 40 for weeks and kept getting that ugly convex bead with cold roll on one side, and I kept messing with heat and travel speed when the whole time my rod was laying back way too flat. Old timer on the job told me to stand the rod up more and push it in tight, and it was like night and day, bead just flattened right out and the toes wet in nice. I run downhill roots around 15 to 20 degrees off vertical now depending on the gap, steeper when the fit is tight. Key is you gotta keep that rod jammed in the root so the arc digs in instead of skating on top. Funny how the fix is almost never the machine or the rod, it's usually the angle or the guy holding it.