Mike,

One of the articles indicated that this advantage was lost if the angle of attack (direction of water vs. direction of riblets) increased over 15%. I would guess that the bobbing up and down of the boat would cause large deviations of the AOA, which would reduce the efficiency.

Also noted was the increase in total wetted surface caused by the riblets, which if memory serves, increases drag... Do the benefits outweigh the drawbacks? You be the judge.

Interesting discussion nonetheless....