[frugalfisher]

I agree with tail roping and gill cutting. If you were able to gaff a medium or large thresher you would be swimming! Or have a broken gaff. Sharks are real pros at spinning when gaffed. I've been pulled over twice when grabbing tails also. I like slapping it a few times if the hook is set well to make sure it is not green when you grab.
I attached proof of concept photo.

Good Luck!!
James