[lunarhighway]

i'd say look underneath and see what needs smoothing there, the underside is likely the most aero crude surface and you can't see it so you'r work doesn't have to be perfect, if you give anything a shot of black paint nothing will appear odd.

you may also look into installing additional side skirts, i'm thinking plasic L brackets and 3-4 screws in the bottom of the existing on, perhaps the new skirts could be further inwards still keeping the airflow undreneath the car straight, but less visible from the sides