The Sony Xperia Tablet Z is now available for pre-order in the United States, and is set to start shipping on May 24. The tablet is 6.9mm thick, and weighs about 17.4 ounces. It has a 1.5GHz quad-core snapdragon processor, Android v4.1.2 Jelly Bean, with a planned upgrade to v4.2, 16GB memory, with 2GB RAM. The tablet also has an …