So many questions today!
Engine compartment. Piece of tin at the bottom of the compartment right aft of the engine, has two holes for the air ducts to pass through on the way to the heater boxes. Even more aft of that is another piece of tin that goes all the way to the back of the bus, then outside, and folds downward. It effectively forms the floor of the compartment. It is held in place by two (on my model) bolts above the bumper. It has the hook thing that the door latch latches to.
At the front edge of this tin, where it meets the tin that has the heater ducts, are two rubber lips. How are these meant to be aligned? Both under the forward tin? Both above? Or does the forward piece of tin rest gently -- nay, lovingly almost -- between the upper and lower rubber lips?