As others have said a skeg will not help stability (other than directional stability i.e. tracking).

For tracking you will get the more effect the farther towards the stern you put it. But you don't want it so far back that it comes out of the water in following seas. This usually means 1/2 to 2/3rds of the way back from the cockpit to the stern. A skeg for tracking does not need to be very big for good results.

> Currently building Great Auk and am interested in stability potential of a
> retractable skeg. I have used a centreboard/trunk setup in a 17' sailboat
> and wonder if this concept would aid in stability of the kayak. Where to
> place, size, daggerboard or pulley operated - which way to go? Nick, your
> book is the best I've seen and read. Many thanks.