I have not had any problems with the old narrow or new Road King/Trailex trailers. I have used both the 8" and 12" tires up to highway speeds. From Prius to Tundra they have done well on long trips.

I have never used a stock road trailer, I built mine custom from welded aluminum C-channel because I’m a knucklehead. I have had very good luck with the Timbren axle-less suspension that etrailer sells. I tried another type of torsion axle early on (Flexrite) which did not do well after a couple years, but the Timbren solves a major problem found in the cheaper types of torsion axles: the pivot mechanism is all steel, the torsion damper is not part of the pivot design (if the rubber torsion damper goes soft in the cheaper type, the wheels go out of line, and you burn up tires FAST). So, the Timbren isn’t cheap but very well worth it, I have logged a lot of miles on mine. I also went to larger radial tires and am happy I did. It’s the fact that these are torsion axles which is the big plus, the damping these provide means they won’t oscillate on every bump the way leaf springs do. The axle-less aspect is not terribly important unless you’re planning to haul off-road (bad idea). In fact, you can place a 2” square tube across the two Timbren units to force them to start nicely aligned, which I did (did I mention misalignment was bad?)