Congratulations on your new Snoozy. I had a friend fabricate a spare tire carrier that was welded to the frame, and does not involve the body. The factory has a mount that bolts to the frame and through the body wall in the kitchen area. Contact a fabricator/welder in your area to see what it would cost. Some people carry their spare in the shower, while others carry it on the tongue or in the tow vehicle.
Dave & Paula