chicago pizza dough problem

I have been trying to make a Chicago deep dish pizza for over a year.  I have tried copycat recipies with so so results.  The biggest problem I have is the bottom of the pizza and the crust edge getting done, too brown, before the middle is.  I have tried different temps (my oven only goes to 500), rack heights, pizza stone underneath, cast iron pans etc.   I have no problems with thin pizza as I pre-bake my crust for a few minutes and keep my moisture levels down on veggies etc...