Having pulled heavy GN/bumper pull/5th wheel and pintle trailers for a living I found the size of the tow vehicle makes no difference if the rig has the tail wagging the dog issues. Its not just a matter of drivers experience or too small of a tow vehicle.
I've seen 40' pintle hitch enclosed vans (axles in the center like our RVs) behind single axle class 8 tractors or my one ton DRW trucks with severe sway issues.
The 40' enclosed trailer/pintle hitch I had in service was bitzh to pull with any of the trucks we had. Myself and my drivers hated to have to be the one who had to move it to the next job site.
A class 8 tractor pulling semi trailer/trailer have nothing in common with a bumper pull TT as in the case of this discussion with the axles in the center of the box and the ball on the tow vehicle extended well behind the tow vehicles bumper. IMO a poor choice for comparing or as a example.
I don't use a anti sway device but I've been around long enough to know there are lots combos out here that needs them. Every one doesn't own the equipment you or I own so making a claim a anti sway devise isn't needed isn't the way the real world operates.
