I noticed that the gutter's end lets the water leak down into the ventillation area and ultimately down to the bottom where it pools up and start the rusting process of the seam that will be visible soon on the rear bottom side.  That small body panel at the bumper ends seem to have the victim of the leak down.
I think, if one extends the gutter and let the water leak by the rear hatch, it will not do as much harm.  
A lot of cars that have just dew run off in the morning got the rust unnecessarily.
What say you?
Zoltan