Yes, while the box and cab are mounted on the same frame, the frame is not THAT rigid. Just watch in the mirror as you slowly cross a speed bump diagonally. The box and cab will move a fair bit up and down from one another. Easier yet, just jack up one corner, even just a few inches and you'll see what I mean. A rubber hose will, of course flex and if you are only going to be driving it on the street it will not flex much but, entering approaches to parking lots or gas stations can sometimes create some twist. Don't know if it will hamper your ability to run the filler between the cab and box but just something to be aware of.
