USPS. I bought a custom seat for my Goldwing and it cost almost $100. to ship UPS and just a bit under that for fed ex. USPS carried it from MA to AZ for $48.65 the guy sent it 3rd class. Took about a week and a half, but no biggie.
I guess those are the breaks when you want a seat called the "Road Sofa" ! I must say, it really is more comfortable than any seat I have ever sat on, but that is one big, heavy , thick fiberglass based MoFo.