> the safe manoeuverable speed increases with weight
The reason this is true is because at a higher weight, you'll stall at max deflection before you can put enough stress on the airframe to be a problem. That is to say, at a given speed a heavier airplane will fall out of the air [hyperbole, it will merely stall - significantly reduced lift] before it can rip the wings/elevator off [hyperbole - damage the airframe]. That makes it questionable whether heavier is safer - just changes the failure mode.
The reason this is true is because at a higher weight, you'll stall at max deflection before you can put enough stress on the airframe to be a problem. That is to say, at a given speed a heavier airplane will fall out of the air [hyperbole, it will merely stall - significantly reduced lift] before it can rip the wings/elevator off [hyperbole - damage the airframe]. That makes it questionable whether heavier is safer - just changes the failure mode.