[aerohead]

Are you placing the '5th-wheel' position through the hatch and over the rear axle,or just doing a receiver hitch?
If you're doing a receiver hitch,you might just find a salvage Insight rear fascia and cut a hole in it to allow a modified Thule receiver to penetrate through it.There would be no need to mutilate the diffuser/valance area,which if you do,will negatively affect your highway mpg.