>>>>>Did you have a chance to check the actual trailler weight of your PS. My car has a 1.3L engine and a fair amount of road steepness has to be overcome.>>>>>>>

On a 250-pound aluminum Trailex trailer, the total tow weight is about 1,050 pounds.  A cheaper galvanized trailer will weigh 600-800 pounds so you're up over 1500lbs total.   That's going to tax a 1.3 liter engine and its transmission.

Depends a lot on the car. Phil Bolger published an enlightening article about towing big trailers with very small cars.  Ramp launching is going to be the biggest challenge, maybe insurmountable.  Bolger got past it by unhitching the trailer, turning the car around, and lowering the trailer down the ramp using an electric winch mounted on the front bumper. 

A creative solution, to be sure, but there's the problem of staying in control on the highway or on hills.  If the trailer wags the dog, you could crash.

When I say four cylinder cars, I'm thinking of a Subaru wagon or similar.  I'm towing with a Honda Element.  2.4 liters and no trouble at all on steep ramps, etc., plus mileage in the 20's when towing.

As has already been mentioned, my view is that the biggest problem in towing is not horsepower, but transmission durability.  Perhaps surprisingly, an automatic tranny is more likely than a manual/clutch to hold up to the rigors of towing.  But the transmissions on small cars just aren't built for much towing.  Even a small car will likely have enough horsepower to get a smaller boat like a PocketShip moving.  But the heat builldup in the transmission will cause quick damage without additional trans cooler capacity.  Additionally, with a simple trailer and an added 1000 lbs, brakes and stopping distances become a factor.  In contrast to electric brakes on campers and utility trailers, many boat trailers can be equipped with simple and reliable hydralic surge brakes.  Many states may require them on a tow rig as small as 1000 lbs.  Also, while the PocketShip and trailer is not yet approaching equality to a typical tow vehicle in terms of weight,  when a boat does come close to equalling tow vehicle weight, problems arise at a steep, wet, mucky launch ramp.

 Over the past year, I've gained some towing experience with a Saturn VUE and a Sea Ray 175 sport boat.  The VUE has 250 hp, which is plenty of get up and go for the Sea Ray.  And the AWD has come in handy at a couple of slippery ramps.  Stopping distances become significantly longer when towing, however.  In my state, the trailer is not required to have brakes, and doesn't at present.  But a simple bolt-on kit is available, and I plan to add that in the near future, in the interest of safety.  The VUE also has a factory-installed transmission cooler, but I would upgrade that if I planned any long distance towing.

Finally, I thought I would pass on this warning of what can happen when  you have insufficient towing capacity.