Thanks for all the info. It turned out to be super easy on the west coast trains. I did not have to box or disassemble the trailer, and I only paid $5 and they wheeled it on like a suitcase. They just asked me to make sure it was battened down well. Also, it had to weigh under 50 pounds, but that was pretty easy to deal with, given that they allow three checked items - just pull the heaviest thing out and have them take it separately. For me it was a bag of food. Any other odds and ends can go into a carry-on bag.