Fast2home, I haven't seen any 7' or 8' tall pitchers. The circle is however 8' from the rubber. Even for a 6' tall pitcher landing on the circle would be 133% of her height.
Mark, interesting, I guess there are lots of ways to teach. We just had a conversation last week about this with my daughter's pitching coach (who is pretty well known and respected in Ohio) and he told her she has to work to get her stride foot at least as high as her knee. DD is a sophomore and been pitching a while though. I agree its not an exact science and has to come along little by little. Last year, we were working with a different coach who is also well known and she had her students pace off seven steps, mark a line, and then work on striding to that point. The girls there were about 7th-9th graders, so 7 paces...maybe 6-7 feet is about 125-130% of height.
Do you know if Bob Pele or Doug Finch have published any instructional materials? I'd be interested in reading what they have to say.