Increasing heat retention

I want to bake and roast in my oven as well. I have the 6 lb ceramic blanket. Will the 8 lb doubled make a significant difference? Is there anything I can do to the floor to increase heat retention?

Out of curiosity, what is the average tone to return to ambient temperature at 70° from a 900° fire?

Build is about to begin and I want to make sure I’m making my final decisions wisely!