I've been setting up my side
mirrors just like
MShadow suggested above for quite some time now, and, indeed, there are no spots that aren't covered by either the side mirrors or the
rear view mirror.
However, a word of warning: instead of turning your head when changing lanes, you must now look in two mirrors: the (overhead) rear view mirror, and one of the two side ones. You still can't change lanes safely based on what you see in the side mirrors alone. This is because you are, in effect, moving the blind spots of the side mirrors behind, in an area that is now covered by the overhead mirror.