I think of a kayak as pivoting from its lowest point. Your thinking is absolutely correct about the central location and more control. I have been using the central skeg for 10 months now on two different kayaks. All your doing is shifting the pivot point from slightly forward to slightly back. I now think of a stern skeg as locking up the rear and limiting my control. Your thinking of a central skeg and a strong rear keel line has two different things competing with each other and the answer can vary.

I just uploaded a short video showing edge control with the skeg deployed in the first part and then retracted in the second part. You will notice that with the skeg up it turns only when initiated and with it down I can stop a turn and reverse it.

http://www.youtube.com/watch?v=9MCHHwr6MYU

Sea Kayaker recently tested a kayak with the Skeel or central skeg for an upcoming issue. I am very curious about their response to it.

And in the interest of full disclosure, I have worked closely with Sterling Donalson on this system and yes I am very partial and biased to it.
http://www.sterlingskayak.com/

If you happen to be in the PNW and would like to try it, please let me know.

Best,

Reg

PS.
It has also received a smile of approval from Matt Broze.

: I have two or three boats into which I plan to install skegs. For
: practical reasons (access), they will be located farther forward
: than is the case with most production boats. Intuitively, this
: more forward position seems right, as the skeg would have less
: leverage on the boat and the amount of skeg deployed would be
: less critical. By that I mean it would be easier to get just the
: right amount of trim required for the conditions at hand. What
: I'm wondering is how different positions affect the
: tracking/edge turning equation. I will try to explain: when I'm
: surfing back downhill on a big day in one of my skegged boats,
: it seems that just a wee bit of skeg helps or reduces the
: broaching effect, but still allows the boat to respond to a lean
: or edging. Is this because when the boat is edged the stern
: releases somewhat and allows the chine or asymetrical shape of
: the immersed hull to initiate a carving action? If the skeg is
: located farther forward, might it not release? If the skeg is
: located farther forward there might be more skeg deployed to
: achieve the desired trimming effect than there would be if the
: box were aft.

: One of the things that got me going on this was some research I did
: last week on Mariner kayaks. Though they're not in production
: any longer, there's still a great website to brouse. It seems
: that they were able to use a longish fixed skeg that solved all
: of the usual problems, but did not interfere with edged turns.
: To duplicate this effect on another boat would require some
: trial and error, and in the long run, it might be easier to just
: install a retractable skeg, but this tracking while flat, and
: releasing while edged thing that they achieved, got my little
: brain started...Any thoughts you guys?