The drive carefully comments always make me laugh. You can always drive carefully when overloaded... But what happens when an emergency swerve or stop has to happen? Is the overloaded suspension, frame, steering, tires, etc up to the task? Those are the times you cannot prepare or plan on, and they can easily be out if your control.
I don't list brakes because it's a gray area. The TV brakes are designed to stop GVWR plus a 2000 trailer without brakes. As the TT will have brakes the TV is within it's brake design limits. Now in an emergency the TV brakes have the initial braking power, but the TT will kick in quick.