Quoted from Astropin:How does that explain wide bodies then? They still fit through a standard door.
Actually, it does - kind of. The backbox was obviously the leading part as it has to fit through a door. From there they probably just used a proportion pleasant to the eye when designing the rest of the cab. Later they wanted to put more stuff on the playfield so they made a broader widebody version, sacrificing pleasant proportion for more playfield space.