I've had trailer sway one time many years ago. My dad and I thought it would be a good idea to lighten the tongue weight of his boat so we could set it on the ball by hand. Worked great to the ramps and back for months. Then we took it out on the interstate. At about 55mph, it started to wag back and forth on it's own. No wind or passing trucks. I slowed down and it stopped. Back to 55 and it started again. Cousin piped up we needed to move the boat back forward. Problem solved.
We towed our current 32.5' TT with no sway control for a year about maybe 5-6k miles. Not even a hint of sway. Occasionally a line of passing trucks would blow us around a little but nothing scary. I saw a barely used Equalizer 4 point 10k hitch on ebay and bought it. It took care of the minor push from passing trucks and crosswinds. No hitch will overcome the forces of an improperly loaded trailer. The forces are too great. With TT's being on the verge of tongue light as it is, our rule is we can load anything we can carry into the trailer as long as it's in front of the axles.
