Personally I believe that this is one of the most convoluted methods of installing multiple vehicles within a single resource; as a matter of fact, this would either be a last resort for even achieving anything like the desired effect, considering how inefficient and crude this method actually is. Many of the aforementioned posts already denote the potential issues that this method incurs.
I get that this method is three years old; this one is very outdated, and now there are existing methods of installing multiple add-ons within a single resource which are much more efficient than this one.
I’d even consider attempting this method before the aforementioned one in this thread, but for those that are interested in actually attempting to do this in the least painstaking fashion, you’re free to view my own thread about the matter, and the solution to the issue involving it that I’d been attempting to solve.