We crossed the border about a month ago sans the Airstream - but using the tow vehicle for transportation. We had our normal complement of camping gear under the fiberglass tonneau cover in the truck bed - including two Honda 2000i generators and a small air compressor. I had not declared anything as we were just taking a quick tour of Campobello Island and returning to our hotel in the U.S. later in the evening. We were told to pull over for inspection and when the Border Patrol Agent spotted the two Hondas in the truck bed he came over to caution us that we should have declared them when we went through the border. He was nice enough to say that he recognized the hoses, extension cords, and other camping paraphenalia as normal, along with the Hondas - but the fact that we didn't have anything in tow, and that we were driving a 3500 GMC Dually, is what caused the inspection stop in the first place. He said that they could legally have seized the Hondas! We often travel solo in the Dually but this was the first time we had crossed the border that way. Next time, if we aren't towing the Airstream, I plan to declare everything down to the extra hose washers, duct tape, plastic ties, etc.!
2003 GMC 3500 D/A, CC, LB, 4x4 and 2000 Airstream Excella 30. WBCCI 7074