I'm 6' 2, and use a redged RMC-527 which stands a little over 61 inches tall. Adding in the monopod head and the camera, its about 3-3 inches of extra height. That's enough for most of my usage. I only use it when I have a heavy lens that I am using for hours on end.
I came down with some nasty tendonitis just before having two 4 hour sessions of continuous shooting with both my 200-400L and 24-70. I was sitting rather than standing and walking around like I usually do. The monopod took the weight off my wrists and arms so I wasn't in pain during or after both sessions. I probably got sharper images as well. I have avoided doing much editing of those 2500 images because it really hurts after just a few minutes.