OK, I finally have consistent results. The issue was the Greg's extruder/Hexagon hotend .4 nozzle combination can't deliver repeatable results at 100mm/min extrusion rate. I switched to 65mm/min and the results of 3 tests at the default estep setting of 841 was 24.95, 24.91, 24.95. After adjusting to an estep setting of 884.8 the next 3 test showed 19.89, 20.13, 19.93. Well with the margin of error for the width of the marker I was using to do the measurements. I haven't done any testing between 65mm/min and 100mm/min to determine what the maximum feed rate is for consistent extrusion for this extruder/hotend/nozzle combination, but I'm now confident that at 65mm/min I will get good results. This is why I was baffled by the early testing results and yet had by my standards very good prints. I have always had the perimeter FR set to 65, so it was within the consistent range of the hardware. I may have to get some different nozzles to see if this behavior is nozzle diameter limited, or if the higher feed rate deviations exist in the extruder or hotend. I'm going to do a few prints of items I have already printed at the old estep value to see if I can see a difference in print quality. BTW, the Zenn video showed a 100% FR on the LCD controller, but never showed what he had set as a FR in Pronterface. So I have no idea what FR he was using for the test.