Of course it was more like 1300 miles and not really across the sea but you get the drift. Yikes! These boxes are expensive but the paintings traveled well and arrived unharmed and safely delivered to Peterson-Cody Gallery, Santa Fe, New Mexico by FedEx ground.
The boxes are "Strongboxes" and can be purchased from Airfloat Systems. They have a liner that is as puncture resistant as 3/4 inch plywood and foam padding all around that you can custom cut to fit the work.
The paintings were wrapped in Dartek film that I first learned about from the Mobile Museum of Art when they shipped one of my paintings back to me wrapped in the stuff. It doesn't stick to the varnish in my experience. It can be purchased from University Products.
I taped the boxes shut with EXTREME amounts of Scotch "Extreme Tape", loaded them in the back of my Mazda and headed off to the local FedEx office, where I turned them over to a very nice man and held my breath for the next four days.
Shipping work across country is not for the faint of heart!