As far as I can tell the method of adding meshes can be applied to any missing helper points. This will only work in 2004 and 2006. To produce your own you will need the following.
The Content Creator Guide to give you information on what helpers etc. are needed. I am only describing the outline of my method below.
GMax or similar to produce the mesh. You only need to know how to make, move and texture a cube and add, move and rotate points.
A (recent) traincar whose config file contains a mesh table (unless you know how to rewrite it).
The ability to be able to modify a config.txt file safely. I am not into creating the product queues etc. but copy and modify them from a similar vehicle e.g. another passenger coach, an open wagon etc.
To create the mesh you will first need to create a new folder (I call mine my_mesh) in the traincar's folder. This can be alongside the body art and shadow folders. Make or copy a texture tga file of a single colour into it. I use black and make it 64x64 pixels and call it black.tga.
In Gmax create a small cube say of 10cm side and texture it with your black texture. This is needed as TACS needs a textured surface to export to Trainz. You may need to move it later so that it is hidden in the model.
Decide by looking at the model where you want your helper point(s). I use FileViewer in top view with the grid set at 10cm to help me. Now in top view add your helper point(s) where you think they should be and name them correctly as you go along.
Export your mesh to your new folder as a .im file.
Now you will need to modify the config file. In the mesh-table you will need to add an extra block
load (
my_mesh/filename.im
autocreate 1
)
You will also need to add the correct queue details for your load.
Save and commit (if in CMP) and try in Surveyor. If all is well you should get a load to load when you look at properties. Load your traincar and see what happens. Probably, if like me, your efforts are very much trial and error then the load will not be in the correct place and you will need to go back into GMax and move the helper(s).
As you will see my method is very much trial and error. I am not an able GMax modeller so I'm afraid it is a case of the blind leading the blind. I originally got this from an article on a German Trainz Forum by Vasquez (I don't have the link unfortunately). With the help of Babelfish and my limited knowledge of German, I was able to understand enough to get started.
There are some tutorials out there which are more helpful than the above. Perhaps those more knowlegeable than me can give these links or correct my rather crude outline above.
Remember finally that you are modifying somebody else's work so it is only for your own private use and CANNOT be uploaded.
I hope however this is of some help.