Nowadays I'm exclusively a surfski paddler and have built a couple of under stern rudders so am finding this thread very interesting. I must admit that I don't really understand the benefits of a skeg over a rudder but it is a cool design challenge.
My current project is a surfski based on a modified CLC Pax 20 hull. The S&G cousin of the Mystery. I found that without the rudder it tracked like a train and was difficult to turn so not sure why a skeg?

Thought I might chime in with an alternative solution. integrated rudder.

Mirage sea kayaks are very popular here in Oz and are often used for racing. I have an unfinished OneOcean Cirrus that is getting a mirage like rudder. i have built gas pedal type rudder controls which wll have shock cord attached. Plan is that when the rudder is not being actuated the rudder will stay put sort of like a skeg.

Scroll down link for images of standard and flush versions
http://mirageseakayaks.com.au/other-accessories/