I have a 60 gallon RDS gravity flow tank. Gravity flow is legal with tanks such as RDS. They are DOT certified and so on. They drain into the factory fuel tank and have roll over shut off protection. The sites which sell the models with the electric pumps like to say that gravity flow if illegal. They are right if the tank is connected to directly to the crab or injectors. I guess you mount those tanks on the roof of your truck. Anyway RDS and the other gravity flow tanks marketed today are fed by way of a shut off valve to the main tank. Legal and safe. When I travel I run with my aux tank open and flowing into my main tank when my gas gauge starts to move I know my aux tank is empty. The tanks with the electric pumps work fine and also are legal and safe. The disadvantage for me was they cost a whole lot more and I have another electric pump to replace if it fails. Either way you will be fine. You will also not miss filling up every 250 to 300 miles when traveling.
