[Carl n Susan]

I don't have a dually but I do have a Ford with the B&W puck system. The dually is 2" lower than the SRW model due to the different axle blocks used. I think (I haven't looked for a while) my B&W is set to the lowest point. This still gives me 6" of bed clearance and almost level attitude. On a dually, I would start with the middle position and then adjust accordingly.

I have the arms set vertically over the axle (closer to the cab). There is plenty of room between the RV and the cab window. Additionally there is room to hook up at 70 degrees, or more, with the tailgate down and not worrying about the contacting the tailgate and the RV.