I bent my fins up pretty badly last year and it was a beotch to get the pins out. I had actually compressed the hole the pin goes through and bent the pins somewhat and that coupled with the pressure of the bent fins had them stuck fast.

I spent a bunch of time straightening and wiggling the fins until they loosened up some and weren't presuring the pins so much. I then found a drill bit the same diameter as the pin and opened the holes back up a bit. Eventually, I manged to free up one of the pins and once one side was loose the other pin came out as well.

I think I used up my yearly allotment of expletives on that job.