The rig handles traveling very well. I've taken it on 3 trips recently. The only problem with mine is that it weighs about 80-90 lbs and is as big as a house.
But no clamps loosen or leak or anything like that from riding around in a car. The steel worm-drive clamps I use feel like they're cemented to the tubing/barb.
I used to worry about the same things before I actually built my first water-cooled PC, but when you get hands-on with this stuff you realize how safe it can be. I never worry about mine leaking. Water-cooling is like riding a bicycle. Sure you're scared the first time, but before long it's second-nature to you.