Thanks for the info. This forum has seen so few 2stone grill insert users, that there's nothing to compare it to, but for those kind of BTUs, like I said, the bake times are impressive. I'm positive that the Kettle Pizza insert can't do this out of the box.
My DIY leanings have never lead me to be completely on board with a $300ish 2stone insert, but I've slowly warmed up to the fact that non DIYers need options as well. Assuming the final iteration of your device will be stainless, which will command an even heftier price, but at the same time have that characteristic stainless sexiness, I have no doubt that it will be too rich for my blood, but I'm sure it will make quite a few people happy.
As I look at the photos, I can't help notice that the bottom stone seems to continue to get hotter from pie to pie. Are you turning off the grill between bakes?