most commom breaks are at the bottom of the tank when the mantis is trying to build its new home. they wack at the bottom to try and finish making there burrow. so it would need to be on the inside of the tank to prevent this. the other most common area is the edges of the tank, it is easier to shatter there. another way to help prevent this is to build it a burrow out of PVC pipe, mine loves his PVC burrow and i dont ever have to worry about him smacking the bottom of the tank. but i still have it linned with plexiglass.
when you line the bottom of the tank what you do is use aquarium silicon and lay down a pattern of beads across the bottom, then set the acrylic/plexiglass ontop of the beads. by doing this you have created an open space and cushion to take the blow away from the glass. i hope that helps you out, kind of tired so not the best description i could give.