I've got a rifle safe fitted against my garage wall, 2 masonry bolts through the concrete floor and 2 bolts through the brick wall.
The safe is essentially flush to the wall as required but due to the usual irregularities in bricks there is a space between the safe and wall that ranges from 2mm to 7mm wide depending on the height.
To appease the police inspector when they eventually come to inspect it, based on your experiences would it be a good idea to fill this gap as much as possible with some sort of hard plaster or other strong filler? I can't fit a crowbar in the gap at any point (and we know nothing will stop a determined thief anyway) and the safe doesn't budge at all so it's more a precautionary measure.