Heres a few shots of some fins and rails on boards I have.

This is the fin on my log. Bloody big fin and would hate to get hit by one of these.Notice the 50 / 50 rails.


This is the pivot fin on my ten footer and it seems to work good. When I picked the board up I expected a more modern looking dolphin fin on it but was told these work good. It was screwed in around about centre and hasn't been moved since.