I use a vertical propane metal Char-broil smoker. It uses more propane than i thought it should because of heat loss. I covered the outside with 1/4 inch ceramic tile backer board. This helped but I noticed the outside was still way hotter than I had expected. I was working on the burn assembly and noticed the way the racks are inside there is room to put backer board inside as well. I have bought the additional board to put in and was wondering if there may be some reason to leave it out. I used the holes that mount the rack support and the handles mount holes to attach the outside board. I thought I would remove the outside backer panels and use them as a template to cut the holes for the inside panels. The bolts I used may need to be replaced with longer ones but, this seems a an easy upgrade. My real questions is there any thing in the backer panels that shouldn't be near food?