I flew SW this weekend to MCO, from Tampa. They were VERY picky on carryons. I had a small suitcase and a small sling bag (w/ a dvd player) and my small wallet size purse on a strap. They told me one of them had to be checked or I had to put one inside another. On the way back I had a tote bag, my purse and 'to go' food as we were going to be flying over 8 hours with stops & changes and no time to eat. I was told the purse or the food had to go. Fortunately I stuffed the purse in the food bag and they accepted it. These flights were not overly full. So, if you carry a purse, you can have 1 other 'thing' regardless of size. DD had a small backpack purse, a book and her CD case and although they would all fit at least a couple of times over under a seat, they told here she couldn't have 3 things. The book hanging 2/3 the way out of the purse was fine, tho. Go figure!