I have built and raced a Great Auk. I found it quite squirrelly without a skeg. The stern would swing out to the side requiring several correcting strokes. Often I would over-correct and have to give more correcting strokes on the other side. Never had it out in a quartering sea of any significance, but I assume the worst. I then installed a permanent skeg. This helped a ton when I took it to the 20 mile long Blackburn Challenge race, but again seas were flat, and winds calm. The permanent skeg should be fine for my purposes because both races for which I use it, feature no buoy roundings or tight river turns. If I were to build a Great Auk for touring, I would definitely install a retractable skeg.

The photo above is of the skeg which is roughly 19"x3" freshly installed on the Great Auk.

I bought Nick's plans for a retractable skeg and installed it in a Petrel. It works very nicely.