Anyone have experience with repairing cracked firebrick in their stoves? I have one with the older lightweight firebrick backing and it has cracked in half from top to bottom, around where the pellets fall into the pot. Bad design I think, should have been made of steel like on the Enviro Windsor. So, I would like to know what is best to use to repair this on a Lopi Leyden which has a steel backing behind the firebrick. Thoughts?