Wow, I've been thinking of something like this and here you went and pioneered a build
! Like the other brothers said, get something in between your grate/fire and your pizza stone. After burning the hell out of my firse couple crusts, I used suggestions from several who use fire bricks and make a base for the stone, worked great and my pizza's are turning out much better. I use an Emil Henry glazed ceramic round stone that is made for high direct heat - not just for pizza, I get amazing sear on scallops & blackened redfish! Lodge makes a CI "stone" that looks really neat also. Good luck!