Using a soda can would be a bad idea. How could you have $50 to get the xmod and not a $1.20 to get a proper piece of aluminum if you really want a skid plate? It would be really difficult to get an aluminum can that flat. Plus, it's too thin. Also, you'll cut the hell out of yourself shaping it.
BC, just curious why you didn't have the plate provide some protection for the screw in the bottom of the steering knuckle? I've already busted mine out, and I've read others have too. As it turns out, not having that screw in there doesn't seem to affect performance.