Years ago I bashed a USAT depressed center flat with a Bachmann flat to make a 8 axle heavy duty flat car similar to the one that LGB made. I really liked this car but always thought the 7" long carrying deck was too short so I finally put it to the saw, chopped the deck off and made another for it at 12" long. I used wood to replicate “I” beams and a piece of plexi with about 100 holes drilled through in patterns like the USAT deck had.
The deck was also lowered near 1/2 inch which makes it look a lot better.
Here is a video that tells the story.