Perhaps the particular T962a was just a bad product, but at $WORK we just could not get it working reliably across many types of PCBs- it really required tuning

Perhaps the particular T962a was just a bad product, but at $WORK we just could not get it working reliably across many types of PCBs- it really required tuning the profile to each type of PCB (small, large, black solder mask vs green, etc)- and yes, a colleague spent a day or two installing the cold junction compensation mod. From what I saw- there was just too large variance in IR emissivity/absorption of the PCBA and their thermal properties, which resulted in scorched connectors on one batch and raw/non-molten paste on another batch- with exactly the same profile. I achieved much better results with just a (convection) toaster oven and multimeter thermocouple- I only added PID controller because I started using the oven for drying something as well.