At the bottom of the plastic part of the bumper, there is a 1/2" lip going straight down, and going from one end by the wheel all the way around to the other. I would follow this contour, which looked fairly decent, and find some black screws to screw it together. I would probably taper it slightly on the sides as well, to meet with the tapered corner.
http://image.trucktrend.com/f/roadte...t_tow_view.jpg
sorry, that's the best pic i could find quickly, and it's also a good representation of what i'll be doing this summer.... wanna talk aerodynamics of THAT baby?
OH, and note how the suspension is CLEARLY much lower than the front bumper.