Most horse floats use tandem torsion bar suspension and neddies average around 500 kg each so most floats are rated at 2000kg or more, particularly when you consider there are usually a pair or three up in a float plus the weight of the float itself. So don't discount the capacity of torsion bar suspension.
More than enough for a regular car trailer, although the height of the boat trailer would make the CoG rather high, IMHO too high for a car trailer
