I'm going to say that the position of the Bronco on the trailer is the biggest factor. The tongue weight needs to be 10% - 15% of the total weight of the loaded trailer.
Hook up the trailer to the Bronco and go find a scale and weigh the whole package. Your Torklift hitch must be rated for AT LEAST 10% of that. Park the Bronco on the trailer to arrive at the required tongue weight. I would in fact try for as close as I could to 15% for maximum stability.
Parking too far back and having a tongue weight under 10% will get the results shown here.
Unstable
Stu
