FWIW, the underframe is glued to the carbody with some type of flexible adhesive, ie Goo, and just like the passenger cars, there is only 1 correct way to put it back together. There are no "clips"or ribs to hold car together. you either have to resort to some type of adhesive, or make the screws long enough to engage the floor of the car. Quite the departure from the previous gon types I have experience with. Man, this is turning out to be a much bigger project than I was expecting. Mike, thanx for the idea of using the sheared off top to hold trux on!