Funny you should ask this! We are doing Cyrano and were looking for a stagecoach we could use, a local theater company here in MA has one they used in a recent production of Cinderlla that is flat. I'll try to explain it in words. Think of carving a large peice of styrofoam into a pumkin shape then attaching it to one side of a rolling cart. The front of the rolling cart is made to look like the front of a stagecoach, and inside the cart one places seats for the occupants of the pumkin. A large window was cut out of the pumpkin piece and a bench was placed inside the cart, aligned with the window. This was placed on 4 wheels which rolled, but had no turning capacity so it could only be rolled forwards and backwards, which, in reading about your space might not work, but what about figuring out how to put a large styrofoam pumpkin on both sides of the cart, and somehow covering the gap with a beautiful brocade fabric or something to blend the two together?