For years we have been using this "trucker" tie down ratchets and they really work well. We order these off amazon, we have used 12 footers and 15 footers. Simply measure the distance from your top stern rail around the dinghy and back to the bottom stern rail. That will tell you how long of a ratchet strap you will need. If you need to make up a little you can easily do this by adding a loop of line to the bottom stern rail for hooking to. We do this anyways because the hook will not go over the stern rail 1" ss tube. So we hook to a rope we tie on there.