Of the posts so far, no one has said why the door is located in front of the passenger seat!
If you look at a DP, in front of the passenger's seat is the only place it can go on a front door model. The axle has to be back far enough to clear the generator. The generator is placed up front for balance reasons. This leaves a dead area on both sides of the generator. The dead area on driver's side typically has a steering arm and controls, along with coach electrical panels. The passenger side of the generator is the only place where the stepwell will fit.