I am considering buying a baking stone & would like to know if I get one "cut to fit" how much room (if any) do I leave for air flow around the stone?  the racks would hold a 24"x14" stone if I filled them entirely, but that would leave virtually no space.  Just a small amount in the back where the rack slants up.  Can I maximize this & use it all or is there a minimum amount of room I need to leave around the stone?