A friend of mine has sold me enough 3 1/2" soapstone bricks to place under the firebricks. he has also suggested splits on top of the full firebrick for the cooking surface. he has built many commercial pizza ovens and residential ovens over the last 40 years using this method and he highly recommends it. he is a very experienced hobbiest bread and pizza maker as well. I enjoy his enthusiasm and advice. But some on this site have concerns about the lack of FB insulation underneath the bricks. I don't think my friend would steer me wrong however I would like to hear from other experienced oven builders. what are your thoughts? thanks for sharing.