I've installed three or four of these on Cobra trailers. Very well made and nicely designed. I put them on both single place and two seat glider trailers. They are pretty effective at controlling sway, even though the customers all tow with full-size pickups or SUVs. It definitely helps when towing with a short wheelbase vehicle.

I can't say how effective they are with something like a VW Golf, (but I consider that to be too small to tow a glider anyway. Maybe the wagon, with the longer wheelbase will work better.) I know they tow with tiny vehicles in Europe, but the glider trailers all have an 80 kph limit over there. Here in the US, 75 mph freeway speeds, crosswinds and passing eighteen wheelers are going to make towing a pretty "sporty" adventure. Keep an eye on the rear view mirror. If the trailer changes lanes, try to stay in front of it ;-)

You do have to use an actual 50 mm ball. A two inch ball is too big for the clamping action and 1 7/8" is too small. Remember that it's unlikely that anyone else will be able to tow your trailer unless they also have a 50 mm ball. Order an un-plated (stainless steel) ball if possible. Chrome plating has a tendency to start flaking off under the clamping loads while turning.. Lubrication is NOT permitted, as it negates the clamping friction that controls sway. Another issue is making sure the ball CANNOT turn and loosen the nut! No matter how much torque you put on the nut, it can still get loose. In Europe, the ball must be welded to the hitch plate. I usually machined a flat spot on the base of the ball just above the threaded shank and welded a piece of steel bar stock to the hitch plate.

Hope this helps.