No, I'm not involved with leaderfins, but a friend is the local dealer and I own a couple of their fins, so I know them quite well. I've mostly built up knowledge of fins over time and through owning lots of types of fins.

Your points above are very good ones, I was only taking top speed into account and only looking at blades. Obviously this is only a small part of the story. I do disagree with you about fibre fins having bad stabilisation and manuverability, but that depends on what you've tried. Of course it depends on how you make the fin as to what properties they have. I firmly believe that fibre or kevlar blades are the way to go. The key is to take those blades and get the rest of the story right too.

In saying that, alas are quite a good starting point. They may be a little wide for my liking, but they balance all the variables quite well. I think it would be worth experimenting with side rails, 1cm above and below the fin would be a good starting point. For some wide examples, see C4 Falcons and Mustangs, while the Fisher Power Fins have a much smaller rail.