I once proffered the notion that there should exist bikes for the taller riders that were proportionately larger in all dimensions, including wheel size.
It was pointed out to me that the energy required to accelerate and maintain speed of a larger (say, 32") wheel would be far greater than that for the 700c wheel. Kind of a rotational mass problem. Thus the rationale for tri-guys turning the 650c setups.
Anybody for 20" sew-ups??