Great idea! This could be a very good mold for hemp-crete, as it adds fiber to the mix and will stop cracking/crumbling in the thinner sections. You could also add pulverized styro-foam to increase insulation qualities of the brick and also reduce the weight. Thank you for posting!
You would do better and smarter to use stainless steel strip hinge on 3 corners and use 2 clasp on the 4th corner you could just un wrap it or hinge on opposite corners and 2 clasps on each opposite corner