I tow a 19ft "ultra-Light" single axle trailer with a 6 cyl Trailblazer (about 3400lbs loaded)... used to be a ***** especially when the big rigs blow by. Now it tows just fine. The secret is tuning the rig. In my case that meant tires on the TV (the LT variety), tires on the trailer (Kumho Cargo tires), air bags in the TV rear springs (run at 30 psi), adjusting the down force on the E2 hitch (more is better) and running all the tires at near max rated psi(50psi on the TV and 60psi on the trailer) Also empty tanks except forward water tank at half full and propane bottles full. Oh one last thing, two batteries mounted forward of the axle.
We generally keep the speed down near 60mph but it tows up to 75 or so without a problem except that the fuel mileage sucks.