I have a request for a Dr. Who cake for the end of the month. They want me to make the phone booth.  I'm having trouble figuring out what size I would need to make to feed 15 people and what kind of frosting would be good to cover the cake. I was thinking fondant but I'm not sure how difficult it would be to cover this kind of cake and if the fondant would be to heavy. I wouldn't want the cake to collapse as they are trying to get it home.