Can someone explain how to remove an O'Fish'L fin?

I’ve got a project board with one missing fin, so I’ve been thinking about popping the other side out and riding it as a single fin. 

The problem: I can’t figure out how to get the side fin off. I checked the O’Fish’L site and some links that glossed over it quickly but this one isn’t budging. 

 

Any special tricks I should try?

Hopefully,  lay board on it's deck take a rubber mallet smack it hard enough not to overpowering , good solid hit upward on the curve under the tip, works usually with both the old style and new style ofishl, might need more than one hit, but be easy, could have salt and sand inbedded in the sides of the boxes ,  good luck....

Do what surfgypsy says, but not too hard or you may break out the box.  Spray some penetrating oil around the fin if it still won’t budge and try again.

https://www.youtube.com/watch?v=tfzSCavARz0&t=4s  

https://www.youtube.com/watch?v=Wqj4laAtrqU&t=2s

Yup.  Do as prescribed.  I have quite a bit of miscellaneous O’Fishl stuff that someone gave me a few years back.  If you need something PM me.

pull clip in back of fin towards tail with flat head screw driver, Rubber mallot back of fin up and toward nose. Relace boxes with Futures boxes or find side fin set with new z clips on ebay

good luck