I'm usually "all in" when it comes to analysis and experimentation, but I believe you all be getting wrapped up in an exercise of futility. Here's why... The autotune is designed to "learn" the characteristics of your particular smoker, and should never have to be changed, once it's dialed-in and accurate. The "meat load" does not matter; if it did, you'd have to change your tuning settings with different smokes. My 1503CPH unit has undergone one autotune in the last 1 1/2 years, and is dead-on accurate no matter what I'm smoking with it.
Now, will there be times when the autotune results may have to be "tweaked" a bit? Sure. I know some have had to do it, but I'm not sure why. The bottom line is get it where it holds within a degree or two and don't mess with it anymore.
I also believe the heat sink used during the autotune does make a difference. You need something that will absorb heat (like meat does), not reflect it (like foil does). This is why the dry bricks seem to work best. They'll heat up, and retain heat like meat does, so the box temp will be more stable during the on/off cycles.