I have an RDS 45 gallon tank. Fits against the cab and only take up 10” of bed space, doesn’t extend much above the sides of the bed either. Mine is gravity flow into my main tank. I’m a little paranoid about running out of gas and I get nervous when my needle goes below half on the gauge. True panic sets in at 1/4 tank. The extra capacity helps to ease my mind.
I enjoy stopping at rest areas and travel centers more than truck stops, so I also have more options there. Most of the time I buy fuel while out and about and don’t have to when the trailer is attached.
My next truck will also have a larger than factory tank, maybe in bed, maybe a titan.