I was looking for that and couldn't find it. I thought it was 10 mph but didn't want to quote that. Honestly I find that hard to believe but at the same time these were very small round hulled boats with very skilled paddlers so it may have been very possible.

I can find nothing that shows that a SOF would be inherently slower than a hard shelled boat. There maybe a reason and I just have not found it.

The key to a SOF being fast or slow is going to be its hull shape. My 15' Curlew design will kick myr butt if you try to paddle it at or above 5 mph for any length of time. The resistance just gets very high very quick above 4.5 mph. Yet my Long Shot I can paddle at 5 mph relatively easy. I am not in great shape and I can't maintain that for long but I can paddle at that speed for a while. The difference there is the hull shape.

There are LOTS of variables and I just getting a grasp on the basics. I am just not interested in racing so I am not interested in digging into the finer points. But I just think SOF is automatically a slower boat.