At what moment the train mission becomes Mission Impossible ?

We're exploring the San Andreas train side mission, and how long the train need to be to make the mission unpassable.
NOTE: Video is sped up 10 times except when the mission is about to end, otherwise it would take almost 2 hours and noone will watch it.
We all know that the San Andreas trains are boring because they only have 2 or 3 carriages, but using some mods we will make them longer and more interesting by adding different type of cariiages. We'll also use the unused box car model. And we gonna test how long and heavy the train can be until we are no longer able to pass the train mission. If You're interested, stay till the end of the video, and if You enjoyed it, please hit that LIKE button, leave any thoughts in the COMMENTS below, SHARE it with your friends, and SUBSCRIBE to the channel.