Hello, I'm building the 36" Pompeii oven and the primary use is for a cooking a couple pizza's and bread. I had a 5" concrete base poured ( not insulated, why I'm asking this question), a mix of sand fire clay and water underneath my 2.5" fire brick. This is already done and the dome is almost 90% complete. I'm putting a 1.5" FB Blanket and insulating concrete on the dome and then filling the enclosure with 6" of perlite. I could have sworn that I read you didn't need the 2" FB board unless you were cooking large amounts of bread or pizza's.Is this sufficient or will I lose too much heat?