Hello, I'm planning to purchase a Macbook Air. My 15' Macbook Pro (at 5.6lb) is way too heavy for me to carry everywhere I go (carrying it in a bag leaves scars on my shoulders). So I was wondering if the 0.5lbs between the 11' and 13' would actually make a difference when carrying it. I'm also wondering how much weight would my bag add up if i included the air's power adapter.