What happens if the TSA guy says no, will you have someone else with you that can take the computer back home and figure out a way to ship it? Here's an idea: Don't assemble it until you get to PR. Keep the parts in their individual boxes and pack them in your checked luggage, except maybe HDD's if you are using them, put in your carry on. Then try to check the empty computer case through TSA. If they say no, and you have to abandon that at the airport, you won't lose your whole rig.