Looks great! Why not cut the cover to fit? I used the heaver paper binder clips on my first try. They worked well and once attached you can squeeze the silver arms and carefully remove them from the clip for a cleaner look. This time I used magnets sewn into the hem to hold tight to the body. They almost work too well as they want to stick to the frame when I'm putting it on. I made mine out of 1/2" EMT but you wouldn't have that problem with the copper. As for the hole I would suggest filing the edge of a scrap of copper pipe sharp and with a piece of wood backing using it to cut the hole. That should give you a nice clean edge. The heating and melting would work if the cover isn't fiber reinforced.
Good luck and stay dry,
Michael
Good luck and stay dry,
Michael