This answer told me what I wanted to know - that basically so many of those measurement devices out there are faulty - not just inexact, but downright wrong!! Shame on those who distributed them without scientific testing! I am 5'11" in RL and was quite comfortable THINKING I was 6'2" in SL, even tho a majority of Avs around me towered over me. I am unwilling to 'shrink' to an accurate 6'2" height as I already get enough grief about looking too young.
I have almost completed my 5 stages of Loss, and come to acceptance that I must be happy with a 'relative' value of a realistic height. It seems to me that furniture designers in SL would have tried to scale to Real World heights of tables, chairs, etc. - I guess I was wrong! :-(