When you cook pasta, something you have to mix the pasta in the pan with olive oil and various ingredients. For example, in this recipe: http://smittenkitchen.com/2010/02/spaghetti-cacio-e-pepe/  Afaik, there are 4 grades of olive oil, which one should I use in this case?  I've heard that extra virgin olive oil have low boiling point, and the nutrient goes away upon high temperature. I have only a bottle of olive oil which is extra virgin olive oil. Should I use some lower quality olive oil? 
I know this is an old question, but since I have been recently looking up the 'how to's' of ciabatta (which is how I came upon this question) I thought I'd pass on what I've picked up through recent reading and practice.  Stretching the loaf out long-ways is an important stage of shaping a ciabatta, it seems. I imagine that everyone finds that the middle tends to be fatter when yo finish basic shaping, that's just the nature of trying to gather any flowing material into a stable form.  So, carry out the shaping to the stage you have it - but possibly leaving the whole thing a little wider and shorter to start with, but then quite firmly but gently, lift the dough in the middle and ease it out first to one end then the other, until the middle has thinned down and you have a slightly more strap-like shape.   Remember that the bread was invented as an Italian response to the domination of French baguettes in the sandwich market, so it does belong to be a distinctly long and narrow loaf, even if slightly less so than a baguette. 