-- Last Updated: Nov-08-12 6:40 PM EST --
"From a hydrodynamic perspective, does a deployed skeg increase the effective waterline length of a boat, and thus increase the (effective) maximum speed and/or add more efficiency? "
Increasing the waterline length itself won't give you more speed/efficiency.
It's when your increase in length resulting in decrease of waterline width (given the same displacement volume), then you'll have a more efficient hydrodynamic shape.