Had the 2 inch & 200 kg OME lift on the rear of my GU for 6 years with no problems. Used to tow a boat on occasion, not much sag at all even when fully loaded. The ride is pretty stiff when not carrying the Engel, water, tucker boxes & nearly no fuel in the tanks even with the rooftopper on. 400 kg might be a bit stiff & uncomfortable when empty.