The problem with bolts is it takes a lot of them, and they stick out and are in the way on both sides. Sure, button heads look better than a typical hex-head cap screw, but you still have a dozen ugly nuts and washers at each corner on the inside to catch yourself or clothing on. Not good. If you don't want to weld, consider a professional quality panel adhesive, available from your local automotive paint store. It will work great.