I own a 1997 Discovery and need to tow a caravan up to 2500kgs. The vehicle will cope with the load tow weight but the vehicle's manufacturer's ball weight rating on a Series 1 is only 150kgs. I need to legally have a ball weight of 250kgs on my vehicle to be covered by insurance if I have an accident. Ball weight ratings on vehicles are usually measured when the vehicle is fully loaded and when the load is reduced the ball weight increases. Does anyone know if the 150kg ball weight rating set on the Series 1 was done when the vehicle was loaded or not. The rule of thumb is that the ball weight is 10% of the towing capacity and the Series 1 tow capacity is 4000 kgs. Something here is wrong. Please help I'm from Aussie.