We didn't go out to buy a mirror. Especially not one that is octagonal, around a meter in diameter and weighs a ton. But we did. Here you can see the carefully calculated plans that I used to work out exactly where to drill the holes for the two bolts on which the mirror will fit. Unfortunately, even with this level of careful planning I still ended up with the mirror sat forlornly on the floor.
The extra chunky coach bolts are in exactly the right place on the wall, which is nice. But the hooks on the back of the mirror won't fit over them. Life eh?