Never (not even a hint of) any sway pulling the 15ft that weights less than 1/3 of my TV. Not on bumps, not in cross-winds, bot passing ore being passed by any vehicle. Based on my previous experience, when I got the Jubilee, I thought of mounting sway control bar but, after couple trips, I figure; why bother? YMMV
I had couple cases of severe sway at high speed (my shoelaces stood up straight up) when puling double axle
30 footer with gross weight
that had to be approaching the weight of the TV. After installing sway control bar, no problems. In one case, sway was induced by bumpy road, in another, it was induced by a rapid manoeuvre to avoid hitting a moose.
All in all, I'm convinced that beside proper tongue weight, ratio of weight between the trailer and TV is a VERY important factor.