RE: Ground Effects
Perhaps I should rephrase that, If you took the time to become skilled at fiberglassing, and wanted to make your own GE, the side skirts would be the easiest. I've been tempted to try it, but I need more practice at fiberglass. The front and back would be the hardest, IMO, because of all the curves and whatever design you gave it.
I'd have to do more research, but I think it could be done by tossing a ton of clay on the lower car to mold. Shape the clay into your design, then coat it in many coats of fiberglass, making sure it's nice and strong, then remove the clay, and mount the fiberglass onto the car and get it painted.
It's a TON of work, esp all the sanding that much glass would take. I don't know if that exact process would work, but some friends I know are experts and could help me more with it. But at least you could make it look exactly how you want it to look.