There is a way to solve your problem without trying to edit an MDL file.
Install the free version of Active Camera if you're in FS2002.
Have the aircraft on the ground.
Using the Active Camera controls you can walk around the aircraft, sort like a virtual pre-flight. "Walk" to the front of the aircraft. Keep moving the camera toward the plane until the clipping plane of the camera slices away the front of the plane. Do a screen capture of the screen and you should have a template for your cross-section.
Here's an example of this process done on a Ryan STA.

If the plane is a tail dragger, you can always take-off and bring the tail up and then hit pause. The Active Camera controls still work when the sim is paused.