When loading a heavy goods vehicle, how should the payload be distributed across the cargo bed?

1. Evenly distributed across the floor, with the heaviest items placed lowest and centred over the main chassis axles, securely tied down
2. Concentrated entirely against the rear tailgate to lighten steering effort
3. Stacked as high as possible in the front right corner of the trailer
4. Distributed solely on the outer perimeter with the centre empty