why not take a file and some sand paper and chamfer or round the edges of the aluminum... no sharp edges, no cuts. if you clean it up nice and then epoxy it down to the sheeting, you can run a fillet of epoxy (the squeezeout from the application of your alum. should be enough) around the edge with your finger or a popsicle stick. it should be almost unnoticeable that it is there. I would be willing to bet that if you scuffed the surface of the aluminum with some 80 grit and then wiped it clean with alcohol, the covering would stick to it as well.