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.

Knowing how much you guys like pics of boards here's one my nephew just got for his 21st. It was made by Dain Thomas from Byron. Its 9-4 x 22 7/8 x 2 3/4.
This is a little different to mine with its very kicked tail rocker. The rest of it is pure traditional log with the flat rocker, 50 / 50 rails and heavy glassing. This should really pivot turn well. The rails are really knifey and it feels really good under the arm.
Check the black / white fin. My nephews obviously stoked with it .