the scale will change with whatever you have for documentation. So scale is what your documentation says it is. You match your three views then you are scale. The problem you will find is that alot of documentation does not match . It all depends upon the source that was used. So on to the practical side of things. My eye can spot a deviation in outline a mile away. It just stands out so once my eye sees it, its only funscale. Make sense?, probably not.