Hi 3 tons,
Thanks for the history lesson. All these folks with so much knowledge to share. It's quite quite amazing.
Any controller that require manual tweaking of the MPPT function with a screw that is only accessible from the side of the unit that is fastened to the wall is not "state of the art". The Heliotrope that was sold by AMsolar had that "feature" unfortunately.
tpi's wiring is not likely at fault because even at 12.8 volts the maximum number of amps would be in the neighborhood of 15.6 which even skinny #14 wire could accommodate with little loss.
I agree it would be good to have more information.
The Blue Sky 3024di uses quite different technology for adjusting the MPPT, as do many other fine controllers.