I put the railsounds boards in the area in front of the forward motor. The "floor" of the cab insert will intrude into that area. If you don't use the front zone it shouldn't be a problem. The speaker is in the way of the rear cab insert. Since Lionel's design had these parts attached to the frame they aren't an exact match. I actually don't care what they are attached to, I just want to see something other than the wiring harness when I look in the window.
If you think the engineer side is sparce, you should see the fireman's. They got a chair and an abbreviated signal indicator. There is a full description and layout of the engineers side on the Classic Trains site. I think its a pdf that can downloaded. There was a nice write up on the loco in 2009 Classic Trains. They had a nice 3D cut away. That shell was packed tight with stuff. The frame is nothing but wheels from one end of the frame to the other.
