On 11/12/2017 at 9:48 AM, Bourrinopathe said:

including the modified panthera_cockpit.obj

hi Bourrinopathe, which tool did you use to edit the panthera_cockpit.obj file?  ACD3 or Blender? Is there a tutorial somewhere?  Thanks

It just requires notepad.exe, it is all clear text isn't it?

Exactly. For that kind of modification, you only need a text editor (I'd suggest using Sublime Text or Notepad++).
The commands are defined as properties/attributes for a specific 3D object (set of polygons marked as TRIS in the object file). You can edit those commands to your liking.

I explained part of the process in that post, while I was searching for a solution.
I didn't find a specific tutorial but the specifications of the .obj file format are available somewhere on Ben Supnik's blog (just found it - this should help).

Blender and/or AC3D are only required for editing the 3D models themselves (edit, add, remove, change the properties, etc.).