Beautiful mod! Loving it! Makes a big difference on a medium sized US farm playthrough.
May I recommend changing the rotation limit on the pull bar or making some kind of a configurable option to enable rotation because if your tractor is at all taller than the trailers hitch it lifts the front tires off the ground.
If anyone is wondering how to fix this themselves it's in the 655.xml, line 30.
<joint component1="2" component2="3" node="1>3" rotLimit="0 10 0" transLimit="0 0 0" />
Change "rotLimit" to "0 10 0" instead of "0 0 0" to allow the pull bar to move vertically 10 degrees.