Afidel,
Before you blast me, I suggest you watch the video demonstration in the link below..
HEREIn that small scale video around the 25 second mark they move the weight to behind the trailer axle and sway starts with very little to no input.
Around the 45 second mark, they move the weight back in front of the trailer axle and the sway stops almost immediately.
This video should be a sticky and a mandatory must watch video before folks start towing..
HERE is another video that goes over TW and how to determine and measure it (although on larger and heavier trailers one needs to make some adaptations to the way the common household bathroom scale is used which is not in the video).
For the bathroom scale,
HERE is a good video demonstration on how to do this.