As I noted at the very end of the article, in the little section about horizontal safes, I think this is a design idea that needs to be explored. If I was building a house, I can imagine having a horizontal steel chamber, with individual rifle slots, sort of like this,but twice as many slots and the slotss would be 55" long front to back):
Rifles would be placed in horizontally, as with a wine rack. Mount the thing on a slab of concrete in a loading room, and surround it with brick on the sides. Have a swinging horizontal vault-type door on one end that could be disguised with a false cabinet face. Some of the chambers could have individually locked inner doors, like this:
Then you could put wood on the top and use the whole thing as your loading bench.
It just seems to me that horizontal placement is inherently more stable than stacking guns vertically, and individual steel chambers are way more secure. Many popular gunsafes have Really thin steel on the top and sides. I mean 12 gauge is only .10" thick. You can cut that with a Dremel tool! Remove a 1'x1' square and you can reach in and pull guns out.
With my design you'd have to go through a foot of brick,or reinforced concrete), then you hit the steel. You'd have to make a very large hole in top or side just to get one gun. Even if you,somehow) removed the entire top of the safe, you'd only get one row of guns before you'd have to attack another level of steel. You could cover the end opposite the door with a tool-defeating armor plate.
The only real way for a crook to get in would be to drill the door and that's not going to work if it's made thick enough with armor around the lock box.