Let's say for argument's sake though that you were able to add this extra plane and map the additional prefix texture onto it. The next step would be setting up the running numbers. I have tried this already when attempting to convert the BR Green Class 47 to locomotive D1501, as seen here. In this instance I was simply replacing the first number with a letter, so I did not need an additional plane as we would for the coach prefixes. I created a new "number" texture in the form of the letter D and called number_D.TgPcDx (numbers 0-9 already taken, so had to choose a letter for the filename). I then modified class47.bin, class47_digits.bin and class47_numbers.dcsv to include the running number "D1501" and reference the new texture file as a "number". When I tested the modification, the sim knew that I was telling it to display the "D" texture, however because "D" is not a number, it seemed to want to place a "0" where the missing number was, with the below result. My conclusion here is that the numbering system CAN handle letters, but at the same time cannot handle a non-numerical character and defaults back to "0". Complicated to explain but hopefully you can see what I mean.
In TRS you can have what is called an "attached-mesh", which is a separate shape file that can be attached to an attachment point on the mesh. If no attachment point exists or is conveniently located then it can simply be attached to the centre of the mesh. This allowed me for example to add a major headlight modification to a locomotive for which I did not have the source files. It would be interesting to know if something similar exists for RS.
Cheers,
JB
