Running rough after fuel fill - 8.1

My wife likes to "top" the tank off after the gas pump clicks in our pickup. (I'm in bad health and don't pump the gas any longer) I've heard that this is not recommended, but I've never noticed anything wrong with any vehicle I've ever owned if I've done it in the past. However, our 8.1 will run really rough after we fill the tank, and only when she "tops it off." I assume there's an issue with the fuel return system, in other words, not enough space in the tank for returning fuel, and again, I'm assuming this is why the engine runs pretty rough after technically overfilling the gas tank. What is the design of the fuel return on this truck and is there anything serviceable regarding it?