I recently purchased a home with a masonry fireplace and this is a whole new world for me. I ordered a screen with doors online and it was advertised as being 31" tall. I thought that this would be a great fit for my fireplace, which is 30" tall. However, it turns out that the screen is only 29" tall in reality, leaving a 1" gap at the top of the fireplace. I was wondering, is this commonplace for some functional reason (i.e. Airflow)? Is it safe to have that gap or should I just return this screen and get a new one that completely covers the opening of the firebox? Any insight would be greatly appreciated.