In addition to taking care not to cover the drip rails, also consider all of the edges (doors, fenders, etc.), cowl vents, all of the holes (door latch, key locks, antenna) so that they are "thin" for lack of a better word.
As my painter has taught me, in this case, less is more. Less material is more better, more factory. Less chance of cracks and pops when something is installed and tightened down.