Part x351 (41850) - Body, Racers Driver

[Magnus Forsberg]

Finding surfaces to subfile is always good, but dividing flat quads into 2 symetrical halves is never good practice.
Here is an example of useless vertices that should be avoided.

   

Try to remove these surfaces from the subfile, and then add them in the top level as full quads, spanning from left to right side.