This property sets the offset to adjust the actual lift location from the visible Wing. It exists so that your geometry can be in one place while the actual wing physics are in a different place. This is important if making a plane where having the lift where the wings are would cause the plane to rotate itself without input. In other words, the plane might have a tendency to nose dive while flying along, requiring the pilot to continuously pull up with their controls. By using an offset the lift can be moved to balance the lift forces on the plane (make it equal lift in front and behind center of collision model) and as a result cancel out this tendency and make the plane fly straight.
Using an offset would be the same as adding a template to the plane that is simply the Wing geometry, then creating the wing and positioning it in a separate place without any geometry.
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