I was meaning the amount the windward shroud, and attachment at the hull as well as the hull, were designed to take safely. I never meant that your body weight would make the windward shroud go slack. If it does, then you need to re-tension your rig.
However, I do see how the additional stay will help, so I will be adding one. In a nutshell, the boat was designed for a certain width and x amount of leverage to keep it flat.