I will be fabricating, out of fiberglass, replicas of 1953 Cadillac rear fenders, but much oversized. I have a '53 Cadillac like the one in this picture.
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My false fenders will be 3' tall, 4'6" long and 1' deep and have the distinctive tail fin. But (here's the cool part), only a small portion of the big fenders will actually house the wheel (about 1' x 18"). The cavern will be closed off from the actual dirty wheel area with an internal wheel well. The rest of the cavern will be accessible from the inside of the cabin and the galley. It could house bookshelfs, a closet, tv stand. In the galley, the storage area would be much wider, as the caverns could be accessed from the lower cabinets.The usable space in the cabin would be 2'6" wide, 2' tall, and 1' deep, per side. The usable space in the galley would be 2' wide, 3' tall and 1' deep per side. I'll get some images uploaded soon of this idea.
The concept is similar to the Camp-Inn "tongue boxes" that actually open to the inside.