Bread-Bakers v101.n028.6

Lately I have made a couple of batches of Pita Bread using the recipe in 
Laurel's Bread Book. Although they all puff up satisfactorly, the tops are 
often very thin while the bottoms are thick. Other times the tops and 
bottoms are of equal thickness as they should be. Can anyone advise me as 
to what I am doing wromg?

Thank you,
Dick Carlton
Brookings, OR