Please don't give up so soon.
First, as to the basic recipe you used, it was formulated to have a hydration percent of around 60 percent and to produce a dough ball weight sufficient for a 16-inch pizza. Subsequently, I came up with a similar formulation but with a hydration pecent of around 63 percent. That formulation is presented at reply #86 at http://www.pizzamaking.com/forum/index.php/topic,576.80.html
and seems to be popular with some of the members of this forum. But, either way, the dough is for a 16-inch pizza, not a 17-inch pizza. Stretching out the dough that extra inch may have caused the thinness at the center. Even under the best of circumstances, I have found that I have to be careful shaping and stretching the dough to minimize the possibility of the dough thinning out a bit at the center. If you'd like, I'd be happy to caculate the weights of ingredients for a 17-inch size. Just let me know (including the hydration percent you want to use), and I will post the list of ingredients at the Lehmann site (just to keep all the Lehmann formulations at one convenient place).
Second, as to the pizza screen (I assume you meant Adcraft), professional pizza operators usually season their screens by running them through their conveyors a few times or bake them in their deck ovens to season them. My recollection is that I sprayed mine with a light oil-based spray. I have had no problems with sticking to date, and have never used the spray beyond that first time. With use, my screen had darkened and become seasoned.
Third, when I use the screen, I place it on an upper rack position where it bakes for around 7 minutes or so, following which I shift it onto the preheated pizza stone at the lowest rack position for a final two minutes or so to get added bottom crust browning. If I had a 17-inch stone or a fully tiled area (and a peel) sufficient to accommodate the 17-inch size, I might be inclined to do all the baking on the stone or tiles, simply because it is one step less to go through. Unfortunately, the only way for me to get a large size (16 or 17 inches) is to use a pizza screen.
I'd give it another try, using a slightly larger dough ball for the 17-inch size.