Okay, I'll revisit later.
Discovered - for some odd reason - in scanning the Stouffer step-wedge that my i1 PhotoPro 2 head differs in readings in the whites.
If I "Scan" the step-wedge (sweep), the L values are 8-9 points lower in the whites than if I "Spot" read them into the iProfiler software? I was using the M0 scale, but somehow they differ a lot between the "Scan" and "Spot" reading modes.
The Colorport seems to agree with the Spot reading of the iProfiler software as well, just the Scan mode is way off base.
Oddly, the blacks are within 0.2 of the L values between the two methods, but the whites differ from 86 to 94 in the whites (Spot mode is the higher L=94 one.).
I'm guessing I should use the Spot mode and not the Scan mode for the step-wedge.