I tried to make cookies with my large bar pan tonight. I know that there are timing issues with the stones but I couldn't remember if it was longer or shorter? This is the first time that I've used it without a PC recipe. So I gave the cookies an extra minute or two and they still weren't done. But then they cooled a little out of the oven and I put them back in for another 2-3 minutes. Should I leave cookies in for 5 extra minutes every time?