I wrapped the 550 cord around the tin a couple of times (to the width of electrical tape), then taped it down, and repeated it on the other end.
It isn't the best set up if you want to get in your tin in under a minute, and spend less than 5-10 minutes resecuring it. I came to the conclusion that I should keep the 550 cord elsewhere on my person and apply short strips of electrical tape on the lid, and then use one more strip to tape the lid closed.