Not sure how frequent your bear encounters may be, but you will need an electrified energizer to deter those . If you would have that setup, installed correctly, it would greatly enhance your coop protection.
Many peeps choose to predator-proof the exterior with a hardware cloth apron 2 feet out, and just below the surface, couple of inches. This way a burrowing animal is stopped before he gets very deep.
Going with cinder blocks 12 inches deep I think is also sufficient, and I do see it as more...