We have a majestic pre fab in use 22 years. The chimney cap had leaked and rotted out an area appx. 1/2 inch by 1/4 inch. We had a whole new chase and cap installed. I purchased Dow 2000 degree caulk, and repaired the gap perfectly(as per directions with heat)The whole fire box looks good, however my buddy works with stainless steel and told me he could make the exact size insert for the top, and just screw it in place with stainless screws. would this new layer effect anything in a negative manner. Regards Misterx