I pull a 31 ft TT with two friction bars and a more than adequate TV.
I think it must be discussed... what are you talking about when you say sway?
Most people say the word "sway" but its not sway, its the natural "wiggle" that comes from the TV and the TT as vehicles pass (pressure wake, hits the trailer first, then the TV) This is NATURAL and SAFE.. However, it is uncomfortable.
SWAY is the "tail wagging the dog" nearly uncontrollably,
A properly set up WD hitch (Standard hitches are effective, they are lower cost because the design is OLD. It does not mean that they are JUNK.) properly set up trailer, properly set up TV will NOT sway.
so, before you mess with the sway control.. make sure that you have the WD hitch DIALED IN 100% correctly. After this add your sway control. What you will be rewarded with is a rig that does not sway and does not WIGGLE when vehicles pass or when the wind blows.
My experience went like this.
1) WD set up incorrectly with no sway control. Lots of wiggle, nearly swayed, on the verge of losing control
2) WD set up correctly with no sway control.. No sway, stable steering, etc... but there was significant "wiggle"
3) WD set up correctly with single friction bar... A lot less wiggle, much more comfortable.
4) WD set up correctly with dual friction bars... no more wiggle. very stable, very comfortable.
YMMV.. other sway controls work fine. For me the friction bars are cost effective and practically effective.
And yes, if you are over 26 ft long, it is highly recommended to use two bars... by the manufacturers.
Thanks!
Jeremiah