I finally got my PID controller finished today, and took it for a test run. Works pretty well, but the temp drops from the set value of 725 down to about 685 whenever I add an ingot to the pot. The ingots are roughly 1lb and preheated on the hot plate to about 365 degrees. I was surprised at that much of a temperature drop with a preheated ingot going into the pot. Recovery of set point temperature was fairly quick. The PID seemed to regularly overshoot temp by about 5 degrees. I noticed that the output voltage was turned off below the set point, so it may just be something to do with the pot itself.
Overall, I'm pleased with the results as the temperature of the pot seems more stable. The next test will be with the Lee 4-20 using the ladle.