I am not condoning any of this, I'm just giving you my own personal experience. I had a 1996 auto Outback. We towed a 21ft 3400 lb 1991 Bayliner. It was on a steel tandem axle trailer that must have weighed at least 1000lbs as well. We cruised at 60 with no problem. Suspension was fine, though we had a rear sway bar in. Up the launch ramp was a breeze. She pulled up with barely any pressure to the gas peddle. Only issue was the acceleration up hills at highway speeds. You did have to be full throttle to keep the speed at 60. But that was just up hills in Wisconsin. I now own a 2008 Outback with the 4 cylinder and a 5 speed. I tow 3000lbs, no problem.
I'm not saying it's safe, but I had no issues.