I lugged my H20 rigs to LANs with no problems. I mean I'm not going to say the risks aren't there, they are, but if you're careful and pay attention to what you're doing, it should'nt be a problem. Hell i even transported my Phase cooled rig to a LAN. Tho that was more work as lifting the behemoth into the truck almost killed the family jewels ( LOL !!) , but no sweat. It had wheels ( as most of my computer tanks do
) so just the lifting is where the muscle comes in.
I'm no puny guy (6'1" 190lbs) so it really isn't a big deal. You just have to be more careful as how you transport your pc. This includes not letting your friends carry it or strap it down into the vehicle. One of your friends doing you a favor or helping you out drops it, or any freak accident happens ( which it does from time to time) and then you're ready to kill him.
One thing I learned was when it comes to transporting my rigs to LANs, i take full and sole responsibility if anything should happen, thus is why I carry my own stuff. If i drop it i can't blame anyone. Of course the ppl i do allow to help me are responsible and if anything should happen i know they'll be good for it
This applies to both air cooled rigs and H20 ones. Just pay attention to what you're doing, take precautions and triple check evrything before/during and after the transport.