Is it any coincidence that when I turn on each of P, I and D to be a third of their respective bands, the systems is stable? If so, what is the point in worrying about tuning, just use the full functionality (PI and D) but just turn each of them on to a third of their extent. For example, P range = 10000 so turn it on to 3333, I 5000 1666, and D 100 so turn it on to 33. I did just this with a system I use. Or is this just a fluke and you must tune?