This type of main sheet setup is called a Crosby rig, and it is the absolute worst way to control the main. It how my boat is setup, and I absolutely loath it, adding a traveler is something I plan to do as soon as I can finish with all the other projects that I have been working on.The sheet tackle runs from one side of the stern upward to the boom then downward to the other side of the stern - an A shape.