Yes, after looking at the Alternator Secrets site (REALLY good catch
) and thinking about what we did at the dealership (only full-field at idle) then it would be doing full voltage at a low RPM. It's been over 10 years ago...
As soon as I can capture my son and his Money Pi... I mean GMC (He works for a tree-trimming contractor... 10 hour days...), I'll dig out the camera, load tester, and a non-rusty nail, and play!