I guess stainless is not good for baking as I have not found any threads.
Picking up a 17 x 17 x 1/2" and same size but 1/4 A36 steel plate tomorrow or Friday.
My brother in law found a place that will sell both to him for $20.
I don't think the size is exactly 17", may be a little larger or smaller. But for $20 guess that's a pretty decent price.