Six bikes does not mean one six-bike rack while towing.
This example spreads the load: two lighter bikes on the tow vehicle roof, three at a properly designed drawbar or toolbox carrier, and one light bike on an approved rear receiver. Another useful arrangement is carrying all bikes on the tow vehicle and caravan front, then plugging an unloaded ReVert 4 into an approved caravan-rear receiver purely for rack storage while travelling.