Different strokes for different folks. I plug in the 5th wheel while I'm backing under it during the hitching process with the tailgate down. When the kingpin gets over the tailgate, I stop and plug in the 5th wheel's umbilical to the plug mounted behind the driver's side wheel well - I reverse the procedure when unhitching. I really wouldn't relish the thought of climbing over the bedside trying to hook up a front-mounted plug with the 5th wheel already hitched up, but to each his own....
Rusty