Yes the hole is probably way to big! You can either get a thick piece of aluminum foil and poke the tiniest point in the center with a small needle or safety pin, or get a soda can and cut out a square section, and tap a needle into it and sand it down with sand paper.

vary your exposure time (bracket) on the same shots. and make sure you move the film along far enough to not get multiple exposures or overlapping edges.

good luck!