On Monday, September 7, 2020 at 11:30:06 AM UTC-6, Nick Hoare wrote:
To get back to the original posters question the only thing I would say is
that really they are for make a good combination better not a bad
combination good. If it is not safe without an anti-sway hitch it probably
won't be safe with one, you will just be going a bit faster when it all
goes wrong.

Nick is entirely correct. You can't fix an unstable trailer with an antisway device, but you can make up for a (slightly) unsatisfactory tow vehicle. Once again, MASS + longer wheelbase = better stability. And adding weight to the tow vehicle does NOTHING to increase the stability of the trailer, and the higher loading on the vehicle's rear wheels is likely to make a sway problem worse. (Think: Moment of Inertia.)

That being said, some weight on a lightly loaded rear axle will help with traction, but not stability.