I do believe the brake rotors and calipers are the same. So they fill the inside of the gq wheel, but leave tons of room in the sq.
Just memory from other posts here and in giulia forum. Call me al always comes to mind - he swapped his cc brakes on gq for same size steel - and then bought standard brakes on his sq and switched to the bigger calipers and aftermarket bigger rotors AND used wider 19's from his gq on the sq. Search his posts, he may have used the stock 19's for his winter stelvio set up too.