@supwaxer.
I run the medium size C drive surfboard fins, so they are smaller in size then the Original Sunova fins.
They give me some extra drive and not making the board to stiff while surfing .
The biggest difference for me was surfing backside waves, for some strange reason they are just fantastic for me that way
Maybe its me but I love these and all I can say you should try.
Or drive up to the Netherlands and try mine