Been using the 10.5 Naish Dolphin fin - seems to allow a bit more footsteering and reduces tail-drift - possibly at the expense of a little glide - but I can't say that I can feel any extra drag.
Here is a link to pictures of his new prototypes. Getting good reviews from the Hood River and Maui. He makes others too. He understands what it takes for a fin to perform on SUP's
