Here is an old post:
2 cups KA AP
1 heaping TSP yeast
.50 cup, plus 2 TBS water
1 TSP sugar
.50 TSP sea salt
6 TBS oil (5 canola, 1 extra light olive oil)
Kneaded by hand for one minute, then let rise for 8 hours at room temperature. Then streched it out by hand this time, folded it in quarters. let the dough rest, then repeated folding. let it rest again, then pressed it by hand into 9.5" pan. Added .50 pound Sorrento mozzarella, and 6-in-1-based sauce. Cooked for 40 minutes in preheated 450 degree oven.
The result was very much like Giordano's, so I think that this much oil (6 TBS) is the trick. However, it was almost too biscuit-like, so next time I will knead the dough for two minutes to develop a little more gluten. I would recommned this to anyone who wants to try this version!
This is the basic formula--if you use Kosher salt, you should up it to around 1 tsp. Since I've been doing more trials I think that a 2-minute knead by hand makes a more authentic Giordano's crust. I also don't know if you need to do the folding trick (I got this from Tom Lehman and Giordano's does run their deep-dish dough through the sheeter twice, but I don't know if it makes any difference), and I don't know if rolling it out (mimicking a sheeter)versus pressing it into the pan makes any difference.
As for your leathery experience--the more you knead the dough, the more the gluten forms, and the more gluten you have, the more bread-like the dough will become. I don't know if this is what you mean by "leathery". Traditional Chicago deep-dish (Giordano's, Uno's, Malnati's, etc.) features a biscuit-like crust, which requires a much shorter kneading time.
Hope this helps!