I've been eyeing Titan's
Spare Tire Auxiliary Fuel System. Add 30 gallons to my existing, pathetically small 26 gallon tank without messing up the computer or having the fuel tank hang below the frame. I'd mount the spare on the front receiver or just have it in the bed with the camper unloaded. Getting to the spare with the camper loaded is not something I look forward to having to do by the side of the road.
As to why... One time I was driving through Montana and left the Interstate with just under half a tank. The low fuel light had been on for about 5 miles before I got to the next station.