just reading this thread, it's very interesting! I'm quite new to this and have encountered the same problem it seems.
Culture: 45g (50/50 flour/water)
Mix, then leave for 15 mins. Then knead until smooth and leave for 10 mins. I then covered and left in the fridge for 24 hours. I then uncovered and left out for 3 hours to warm up. Made my pizza and cooked in a conventional oven at highest temp (~275).
I too got a very stiff crust (it was tasty though!).
I think next time (I have 2 more to try tonight and tomorrow night) I will keep completely sealed in the fridge and while warming to room temp.
Does anyone have any ideas? Will the dough always be stiff at this cooking temp? If I can't cook at this temp I shall move onto a NY style.
Any help would be much appreciated