It does not seem to be a concept that is
particularly useful for the solving of problems.

Looks like you haven't thought it through. If one
wants to create a shortened dual-Z0 stub with
equal lengths of each section of Z0High and Z0Low,
here is the corresponding chart for different
ratios of Z0High/Z0Low.

http://www.w5dxp.com/DualZ0.gif

As an example, one can create an electrical 1/4WL
stub that is 1/3 the normal physical length by
using 600 ohm line and 50 ohm line.
--
73, Cecil http://www.w5dxp.com