At least now I'm looking at the diagram!
And I would venture that the boat is not perpendicular to the horizontal plane when you are attempting to right the boat. When you are at that point (trampoline is vertical), you've already cleared most of the main from the water, and righting should be almost automatic at that point (if the boat is facing somewhat windward)
Actually, that's at it's worst point from a pure weight balancing perspective. The center of weight for the boat extends further away from the center of rotation when the mast is horizontal. In the real world scenario, however, wind is starting to get under the sail, providing lift, and helping move the combined weight center move further toward the sailor side of the equation.
