I am not 100% sure John but i think all your enq may come down to nose weight, normally with a car it will be 75kg but a 4x4 will be in the region of 100kg, i know there is a hight the ball must be fitted to and if its to low to the floor then you can have a swan kneck tow ball fitted to bring the hight up a few more inch. I hope anwering to this more people will try to help because i think this is a problem with a lot of units, many a time i have seen a car with its bottom on the floor and the front end of the van only a few inches from the floor, good luck with your enq and i will look forward to reading other replies, should be interesting.