For those of you who have flipped your shackle hangers, what is the secret to removing the rivets? I have spent a few hours grinding the heads off one side. I thought that with the head removed, I would be able to drive them out with a 5# sledge. Unfortunately they will not budge. I would prefer to not drill them out as I want to keep the original frame hole as close to stock as possible. Any help would be appreciated.