Rover
If you followed the guide in Setting up the script, your rover should already have a programmable block, a display and some means of controlling it. The only thing remaining is to set up the rover's trailer hitch, and to set up your default options. The examples pictured here are all small grid, but large grid works just the same.
Please note, this script uses grid identities ("subgrids") to work out what a trailer is. Unfortunately, this means that your trailer hitch must be on the same rigid grid as the programmable block.
At its most basic, the rover's trailer hitch is just a hinge at the back of the vehicle, aligned such that your trailer can be aligned with it and attached using a hinge head.
This hitch is pretty basic; attach and detach controls are somewhere in the cockpit, and there's a handy camera for reversing up to the trailer.
This hinge is more fancy. There's no camera, but there are buttons here so that the player can attach and detach from right here.
These will be lining up with a trailer hitch that looks like this one, pictured looking at the back of the rover.
The hinge that you have put at the rear of the truck will work fine as it is if there's a properly configured trailer coupled to it, but often there won't be. So that the script always knows which hinge on your rover it's supposed to be watchign for trailers to be coupled to, add the following to the end of the hinge's Custom Data using the K menu:
[trailer]
hitch=trueAlternatively, and just as valid (for compatibility reasons), this works too:
[trailer]
front=false