Russell,
You're quite right there, mate!.
I had an apprentice Liney working with me recently.
He assured me, he was cool with hieghts, and that was OK until I asked him to hop up on the top cross-arm (carrying 11kV 3phase), he got up there OK, but, I had to get him down, after he looked down and saw that he was a long way up in the air.
I hate doing Ladder Carry-Downs, without a line, and I normally ONLY do these for the Fire Service!.