Sean, Welcome to the site. I know the TV wheelbase vs TT length has a lot to do on how a TT handles on the road. At what length of TT do you find the Hensley or ProPride 3P hitch to be of real help in towing a TT.
Do you have any guidelines?
I do know of some that have a double cab truck with an 8' bed(long wheelbase) and a 19' TT and have chosen to have a Hensley. I would think this is more of a they feel safer Kind of a belt AND suspenders mentality
Thanks for the welcome!
There aren't really any guidelines established as it can be based on an individual "seat-of-the-pants" feeling.
However, there is a lot more to consider than just the length of the trailer. A Pivot Point Projection hitch projects the effective pivot point approximately 50" forward from the hitch ball. The shorter the overhang on the tow vehicle, the closer that effective pivot point is to the rear axle.
If we take a measurement from that effective pivot point back to the centerline of the trailer axles, we'd have the lever arm working against the tow vehicle lever arm. That is where the length factor comes into play.
Then we have to consider the weight ratio of the tow vehicle to the trailer. A light trailer can sway around back there all day and not affect a heavy tow vehicle.
Then there are tire issues to consider on both the tow vehicle and trailer.
So, as you can see, there really isn't a rule of thumb.
My experience with these types of hitches shows that the greater you can make the difference in that tow vehicle lever arm (shortening it) versus the trailer lever arm (that is constant based on the trailer length/design) the greater the control factor is regardless of the weight and the tires.
I guess I have been a bit long winded here but I see a lot of comments about , "I have a short trailer so I don't need sway control. " That may be true in that particular set-up but it shouldn't be considered a rule of thumb or a guideline for all combinations.