Christian,
I have over 600 hours on the water in my King. It has been in rivers, lakes, bays & the ocean in all types of conditions with wind, currents and seas. It absolutely does not require a skeg or a rudder. The group I paddle with are always amazed that I can maintain my heading when they have to have their skeg or rudder deployed to maintain theirs. With a slight lean and maybe putting a little more effort into one side of the stroke than the other the King runs true.

Best wishes with your build. I hope the pictures in my link help you during your build, and if you have any questions don't hesitate to post on this board or send me an email. I had a lot of help from this forum during my build and would be happy to assist anyone that I could.
Bob