If you must apply a single grade to the note as a whole, I'd recommend using the lowest common denominator, ie VG+. Of course you could describe the note as it is, F front and VG back, providing as much detail as you did in your original post. This of course means you have to use much more space to describe the note, but it does give a more accurate picture than trying to slot the note into the current grading system. I'm of the opinion that the grading system used should fit the note, not the other way around.