A well balanced trailer, meaning reasonable tongue weight(just shy of 100 lbs in this arena). That combined with a level trailer (similar sized tires go a long way toward this goal) will follow you on a good hitch without much drama in any of the cars mentioned. Good shocks and upgraded springs (in the rear esp.) are also easy replacements for safer towing. The goal is to reduce the distance the tongue travels between the ball and the ground. The stiff suspension on the Mini for example is fine. Just be sure to keep the total weight for the trailer package less than the rating on the hitch probably 1000-1500 lbs

The difference between the four 1/8 of a ton club members and the 1000lb trailer is the location of the weight. Put your toolbox and spares in the car not the trailer. My VW Cabriolet is not heavier than the Fit or Yaris and with a sport suspension and nothing else, it pulls the Tornado without problems. It's also easy to see with the top down. I will admit that I really like pulling the boat with my van because of the a/c and space availability for passangers. That brings you right bback to the oil debate on another thread. BTW 22-28 MPG with the Cabriolet 12-14 MPG with the Eurovan with the boat