Hi,
I was using an Emille Henry 14" pizza stone in my performer with great results, that is until high winds in NY blew my performer right off the patio last week (luckily it was off and not being used). The stone was in grill from the night before and did not survive the tumble, having split in two. But before that used it a lot with no problems. It can go right on the grill over direct heat but I got better results using the indirect cooking method. The stone has molded handles on it so we would take straight from the grill to the table. we actually still using the two halves for making pizzas while we wait for the replacement.