The appearance DC used on his last special, I think "Tornado", where he appears on a large sheet of metal under a large piece of material that is lowered slowly from the rafters. Is this in print anywhere or at least the principal or is this a "Copperfield" exclusive?

The principle is definitely in print. However, the presentation and design isn't.

You can get more information by purchasing Jim Steinmeyer's "Theatrical illusion" book (2 combined editions.)

The book isn't cheap, but it's still a gem. A lot of people overlook a principle that still fools people.

Hope this helps.