That one is an oldy from around the sixties.I have ridden longboards boards with hatchet fins.I be lying if I said I noticed huge differences.I think on a longboard,because the fin has a lot of area around the tip,it should stop the board spinning out in a critical situation say like noseriding,or a steep critical wave section.Because there are so many variables in surfing,the best way to see would be to switch fins during the one session ,even then you have to experiment with fin box location.In the sixties all the fins were glassed in so experimentation was all but impossible. I think a lot of things can be learned by playing about with fin shapes and locations.Sometimes you end up with completely different and exciting board at one tenth the cost.If it becomes a dog, back to square one ,no loss.