I think MetroMPG's thread on his rear wheel spats would be useful for you to look into for ideas for mounting on your car.
http://ecomodder.com/forum/showthrea...html#post37306
And a variation on that, alas, without pictures:
I have made unused (as of yet) mounts for my car, that were also made of copper using the same hammer-it-flat method, that I bent with the intent of mounting them with the inner fender liner screws that mount the black plastic inner fender to the inside of fender skin, cabin, frame rails, etc.
I simply bent the flattened copper pipe segments in a vise after measuring out the lengths needed using card or paper for rough measurements
My intent was to make mounts that just needed a simple hole drilled for the mounting screw that already existed, and the piece of copper would be bent and fashioned in such a way that It would reach out almost flush to the fender, that I could mount a spats on the fenders of my car.
Reaching back into my memory, because I haven't time to rummage in the car for where these brackets lay with my tools, they were about half a foot or more before being bent up, as I'd made them to follow the contours of the divot that the fender screw resided, and continued following the fender liner, and the lip created by the sheet metal fender, to the edge.
If you have such mounting holes inside, you might be able to use the same as mounting points for the aluminium bars as supports for your correx/coroplast spat.