Another thing you might try. Add 80% of the flour to the water. After the first rest, then add the remaining 20% flour. I do this as well use a sifter for adding the flour to ensure proper absorption of the water. In side-by-side tests I have run, adding the flour in stages makes for a smoother dough by the end of the mixing. This was originally suggested by marco (user_name - pizzanapoletana).