I was walking around in the Lowe's in the town where I work, after work today, trying to get some more ideas on a UL stove pad/board. I really wanted some of that dense sheeting that goes on roofs, but could only find the expanded styrene (Styrofoam). In the same aisle, came across some Great Stuff spray foam for sealing around windows, electrical outlets etc. Grabbed some of the more expensive stuff that slows the travel of fire, thinking it would be more heat resistant than the regular. We'll give it a try this weekend maybe. Hoping to make a mold, lined with foil, I don't have any titanium foil. I have an old blue ccf pad, but it likes to stay curled. I don't think the spray foam will be too durable, but I'll give it a try. May poke a piece or two of cedar shim in the mold before spraying to give some internal strength.