Howdy Mark!
Just curious, but how much kayaking experience do you have? If you are experienced, then you might as well ignore the rest of my rambling, eh?

So, if you're still here... Ideas...
Maybe you're just pulling harder on the right side. I know, this sounds silly, but, hey... In my 'yak, I can get the boat to track left even on a long glide if my last stroke was a strong one on the right side. I can also get it to track right on a glide with a strong stroke on the left side... I think that this is the weirdest thing - that the 'yak should just go straight and not keep turning. I mean, I've got a deep-v hull! Criminy!

Maybe that was my only idea. Hmm. Still, I thought of another for checking the trueness of your bow (or stern)... Oh. A better idea If you take digital photos from directly above and below you could cut them in half and copy the right side onto the left side to see if you have symmetry. Oh, great explanation. Here's a link!
http://www.adrianbruce.com/Symmetry/split/split.htm

Of course, this would only tell you if you were symmetrical. You'd still have to correct the tendancy in some way. How severe is it? If you shift your seat in the 'yak (permanently!) you should be able to find a paddling position where the turn is corrected... But, you're right, a skeg sounds like a better idea! (Well, for -me- anyway. With your stripped and rounded deck it's likely not as easy to tell when you are off kilter as it is for me with a peaked deck!)

Well, sheesh. Not to be self-deprecating or anything, but I doubt that helped too much. Sigh. Good luck with that!

c